THRIFT-1054. build: explicit call to PKG_PROG_PKG_CONFIG is missing and first use of PKG_CHECK_MODULES may not happen, causes mono detection to fail

Uh, yeah, what the description says. 

Patch: Chris Morgan

git-svn-id: https://svn.apache.org/repos/asf/thrift/trunk@1068976 13f79535-47bb-0310-9956-ffa450edef68
diff --git a/configure.ac b/configure.ac
index b1ab0a7..d5071b0 100644
--- a/configure.ac
+++ b/configure.ac
@@ -24,6 +24,7 @@
 AC_CONFIG_AUX_DIR([.])
 
 AM_INIT_AUTOMAKE
+PKG_PROG_PKG_CONFIG
 
 AC_ARG_VAR([PY_PREFIX], [Prefix for installing Python modules.
                          (Normal --prefix is ignored for Python because