Allow the Thrift compiler to be built without the Erlang generator.

- Use AX_THRIFT_GEN to make configure support --disable-gen-erl
- Update the compiler Makefile.am to exclude the generator.


git-svn-id: https://svn.apache.org/repos/asf/incubator/thrift/trunk@745233 13f79535-47bb-0310-9956-ffa450edef68
diff --git a/configure.ac b/configure.ac
index 040ae06..9a748c5 100644
--- a/configure.ac
+++ b/configure.ac
@@ -162,6 +162,8 @@
 AM_CONDITIONAL([THRIFT_GEN_rb], [test "$ax_thrift_gen_rb" = "yes"])
 AX_THRIFT_GEN(perl, [Perl], yes)
 AM_CONDITIONAL([THRIFT_GEN_perl], [test "$ax_thrift_gen_perl" = "yes"])
+AX_THRIFT_GEN(erl, [Erlang], yes)
+AM_CONDITIONAL([THRIFT_GEN_erl], [test "$ax_thrift_gen_erl" = "yes"])
 AX_THRIFT_GEN(cocoa, [Cocoa], yes)
 AM_CONDITIONAL([THRIFT_GEN_cocoa], [test "$ax_thrift_gen_cocoa" = "yes"])
 AX_THRIFT_GEN(st, [Smalltalk], yes)