thread.c (rb_cThreadShield): make static

Nothing outside of thread.c accesses this variable, so avoid
cluttering up the global namespace with it.

git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/trunk@52478 b2dd03c8-39d4-4d8f-98ff-823fe69b080e

ChangeLog

@@ -1,3 +1,7 @@
+Sat Nov  7 11:40:05 2015  Eric Wong  <e@80x24.org>
+
+	* thread.c (rb_cThreadShield): make static
+
 Sat Nov  7 09:51:38 2015  Koichi Sasada  <ko1@atdot.net>
 
 	* vm_trace.c (rb_threadptr_exec_event_hooks_orig):

thread.c

@@ -75,7 +75,7 @@
 #define THREAD_DEBUG 0
 #endif
 
-VALUE rb_cThreadShield;
+static VALUE rb_cThreadShield;
 
 static VALUE sym_immediate;
 static VALUE sym_on_blocking;