Put __pnacl_real_irt_interface variable in bss instead of common.

Then we don't have to handle SHN_COMMON in the native link.
Normally, pnacl-clang adds -fno-common to force definition
of common symbols. However, the x86 shims are compiled by
nacl-gcc so it showed up.

BUG= http://code.google.com/p/nativeclient/issues/detail?id=3762
R=mseaborn@chromium.org

Review URL: https://codereview.chromium.org/116043012

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@243473 0039d316-1c4b-4281-b951-d872f2087c98

ppapi/native_client/src/untrusted/pnacl_irt_shim/shim_ppapi.c

@@ -90,7 +90,7 @@ static int is_irt_interface_whitelisted(const char *interface_name) {
   return 0;
 }
 
-TYPE_nacl_irt_query __pnacl_real_irt_interface;
+TYPE_nacl_irt_query __pnacl_real_irt_interface = NULL;
 
 /*
  * These remember the interface pointers the user registers by calling the