Mark assembly routines that don't need to be exported as hidden

native_client/src/trusted/service_runtime/nacl_config.h

Index: native_client/src/trusted/service_runtime/nacl_config.h
===================================================================
--- native_client/src/trusted/service_runtime/nacl_config.h	(revision 877)
+++ native_client/src/trusted/service_runtime/nacl_config.h	(working copy)
@@ -120,7 +120,8 @@
 #define NACL_TRAMPOLINE_END     (NACL_TRAMPOLINE_START + NACL_TRAMPOLINE_SIZE)
 /*
  * macros to provide uniform access to identifiers from assembly due
- * to different C -> asm name mangling convention
+ * to different C -> asm name mangling conventions and other platform-specific
+ * requirements
  */
 #if NACL_WINDOWS || NACL_OSX
 # define IDENTIFIER(n)  _##n
@@ -128,6 +129,15 @@
 # define IDENTIFIER(n)  n
 #endif
 
+#if NACL_OSX
+# define HIDDEN(n)  .private_extern IDENTIFIER(n)
+#elif NACL_LINUX
+# define HIDDEN(n)  .hidden IDENTIFIER(n)
+#else /* Windows */
+/* On Windows, symbols are hidden by default. */
+# define HIDDEN(n)
+#endif
+
 #if NACL_ARCH(NACL_BUILD_ARCH) == NACL_x86
 
 #if NACL_BUILD_SUBARCH == 32