THRIFT-3451 thrift_protocol PHP extension missing config.m4 file

This closes #718
diff --git a/lib/php/Makefile.am b/lib/php/Makefile.am
index 309672b..7bb45e4 100755
--- a/lib/php/Makefile.am
+++ b/lib/php/Makefile.am
@@ -118,6 +118,7 @@
 EXTRA_DIST = \
   lib \
   src/autoload.php \
+  src/ext/thrift_protocol/config.m4 \
   src/ext/thrift_protocol/config.w32 \
   src/ext/thrift_protocol/php_thrift_protocol.cpp \
   src/ext/thrift_protocol/php_thrift_protocol.h \