diff --git a/aclocal/ax_lib_zlib.m4 b/aclocal/ax_lib_zlib.m4
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+dnl @synopsis AX_LIB_ZLIB([MINIMUM-VERSION])
+dnl
+dnl Test for the libz library of a particular version (or newer).
+dnl
+dnl If no path to the installed zlib is given, the macro will first try
+dnl using no -I or -L flags, then searches under /usr, /usr/local, /opt,
+dnl and /opt/zlib.
+dnl If these all fail, it will try the $ZLIB_ROOT environment variable.
+dnl
+dnl This macro calls:
+dnl   AC_SUBST(ZLIB_CPPFLAGS)
+dnl   AC_SUBST(ZLIB_LDFLAGS)
+dnl   AC_SUBST(ZLIB_LIBS)
+dnl
+dnl And (if zlib is found):
+dnl   AC_DEFINE(HAVE_ZLIB)
+dnl
+dnl It also leaves the shell variables "success" and "ax_have_zlib"
+dnl set to "yes" or "no".
+dnl
+dnl NOTE: This macro does not currently work for cross-compiling,
+dnl       but it can be easily modified to allow it.  (grep "cross").
+dnl
+dnl @category InstalledPackages
+dnl @category C
+dnl @version 2007-09-12
+dnl @license AllPermissive
+dnl
+dnl Copyright (C) 2009 David Reiss
+dnl Copying and distribution of this file, with or without modification,
+dnl are permitted in any medium without royalty provided the copyright
+dnl notice and this notice are preserved.
+
+dnl Input: ax_zlib_path, WANT_ZLIB_VERSION
+dnl Output: success=yes/no
+AC_DEFUN([AX_LIB_ZLIB_DO_CHECK],
+         [
+          # Save our flags.
+          CPPFLAGS_SAVED="$CPPFLAGS"
+          LDFLAGS_SAVED="$LDFLAGS"
+          LIBS_SAVED="$LIBS"
+          LD_LIBRARY_PATH_SAVED="$LD_LIBRARY_PATH"
+
+          # Set our flags if we are checking a specific directory.
+          if test -n "$ax_zlib_path" ; then
+            ZLIB_CPPFLAGS="-I$ax_zlib_path/include"
+            ZLIB_LDFLAGS="-L$ax_zlib_path/lib"
+            LD_LIBRARY_PATH="$ax_zlib_path/lib:$LD_LIBRARY_PATH"
+          else
+            ZLIB_CPPFLAGS=""
+            ZLIB_LDFLAGS=""
+          fi
+
+          # Required flag for zlib.
+          ZLIB_LIBS="-lz"
+
+          # Prepare the environment for compilation.
+          CPPFLAGS="$CPPFLAGS $ZLIB_CPPFLAGS"
+          LDFLAGS="$LDFLAGS $ZLIB_LDFLAGS"
+          LIBS="$LIBS $ZLIB_LIBS"
+          export CPPFLAGS
+          export LDFLAGS
+          export LIBS
+          export LD_LIBRARY_PATH
+
+          success=no
+
+          # Compile, link, and run the program.  This checks:
+          # - zlib.h is available for including.
+          # - zlibVersion() is available for linking.
+          # - ZLIB_VERNUM is greater than or equal to the desired version.
+          # - ZLIB_VERSION (defined in zlib.h) matches zlibVersion()
+          #   (defined in the library).
+          AC_LANG_PUSH([C])
+          dnl This can be changed to AC_LINK_IFELSE if you are cross-compiling.
+          AC_RUN_IFELSE([AC_LANG_PROGRAM([[
+          #include <zlib.h>
+          #if ZLIB_VERNUM >= 0x$WANT_ZLIB_VERSION
+          #else
+          # error zlib is too old
+          #endif
+          ]], [[
+          const char* lib_version = zlibVersion();
+          const char* hdr_version = ZLIB_VERSION;
+          for (;;) {
+            if (*lib_version != *hdr_version) {
+              /* If this happens, your zlib header doesn't match your zlib */
+              /* library.  That is really bad. */
+              return 1;
+            }
+            if (*lib_version == '\0') {
+              break;
+            }
+            lib_version++;
+            hdr_version++;
+          }
+          return 0;
+          ]])], [
+          success=yes
+          ])
+          AC_LANG_POP([C])
+
+          # Restore flags.
+          CPPFLAGS="$CPPFLAGS_SAVED"
+          LDFLAGS="$LDFLAGS_SAVED"
+          LIBS="$LIBS_SAVED"
+          LD_LIBRARY_PATH="$LD_LIBRARY_PATH_SAVED"
+         ])
+
+
+AC_DEFUN([AX_LIB_ZLIB],
+         [
+
+          dnl Allow search path to be overridden on the command line.
+          AC_ARG_WITH([zlib],
+                      AS_HELP_STRING([--with-zlib@<:@=DIR@:>@], [use zlib (default is yes) - it is possible to specify an alternate root directory for zlib]),
+                      [
+                       if test "x$withval" = "xno"; then
+                         want_zlib="no"
+                       elif test "x$withval" = "xyes"; then
+                         want_zlib="yes"
+                         ax_zlib_path=""
+                       else
+                         want_zlib="yes"
+                         ax_zlib_path="$withval"
+                       fi
+                       ],
+                       [want_zlib="yes" ; ax_zlib_path="" ])
+
+
+          if test "$want_zlib" = "yes"; then
+            # Parse out the version.
+            zlib_version_req=ifelse([$1], ,1.2.3,$1)
+            zlib_version_req_major=`expr $zlib_version_req : '\([[0-9]]*\)'`
+            zlib_version_req_minor=`expr $zlib_version_req : '[[0-9]]*\.\([[0-9]]*\)'`
+            zlib_version_req_patch=`expr $zlib_version_req : '[[0-9]]*\.[[0-9]]*\.\([[0-9]]*\)'`
+            if test -z "$zlib_version_req_patch" ; then
+              zlib_version_req_patch="0"
+            fi
+            WANT_ZLIB_VERSION=`expr $zlib_version_req_major \* 1000 \+  $zlib_version_req_minor \* 100 \+ $zlib_version_req_patch \* 10`
+
+            AC_MSG_CHECKING(for zlib >= $zlib_version_req)
+
+            # Run tests.
+            if test -n "$ax_zlib_path"; then
+              AX_LIB_ZLIB_DO_CHECK
+            else
+              for ax_zlib_path in "" /usr /usr/local /opt /opt/zlib "$ZLIB_ROOT" ; do
+                AX_LIB_ZLIB_DO_CHECK
+                if test "$success" = "yes"; then
+                  break;
+                fi
+              done
+            fi
+
+            if test "$success" != "yes" ; then
+              AC_MSG_RESULT(no)
+              ZLIB_CPPFLAGS=""
+              ZLIB_LDFLAGS=""
+              ZLIB_LIBS=""
+            else
+              AC_MSG_RESULT(yes)
+              AC_DEFINE(HAVE_ZLIB,,[define if zlib is available])
+            fi
+
+            ax_have_zlib="$success"
+
+            AC_SUBST(ZLIB_CPPFLAGS)
+            AC_SUBST(ZLIB_LDFLAGS)
+            AC_SUBST(ZLIB_LIBS)
+          fi
+
+          ])