THRIFT-408. rb: Ruby C extension doesn't build on 1.8.5

This patch redefines the important macros so 1.8.5 is compatible.



git-svn-id: https://svn.apache.org/repos/asf/incubator/thrift/trunk@758517 13f79535-47bb-0310-9956-ffa450edef68
diff --git a/lib/rb/ext/memory_buffer.c b/lib/rb/ext/memory_buffer.c
index e90de75..12dab31 100644
--- a/lib/rb/ext/memory_buffer.c
+++ b/lib/rb/ext/memory_buffer.c
@@ -19,6 +19,7 @@
 
 #include <ruby.h>
 #include <constants.h>
+#include "macros.h"
 
 ID buf_ivar_id;
 ID index_ivar_id;