Merge an important change that I mistakenly left out when merging C99

inline function support. This should fix instances where gcc
spuriously reports the following error:

    error: nested function 'foo' declared but never defined

contrib/gcc/c-decl.c

@@ -798,7 +798,9 @@ pop_scope (void)
 	      && DECL_ABSTRACT_ORIGIN (p) != p)
 	    TREE_ADDRESSABLE (DECL_ABSTRACT_ORIGIN (p)) = 1;
 	  if (!DECL_EXTERNAL (p)
-	      && DECL_INITIAL (p) == 0)
+	      && DECL_INITIAL (p) == 0
+	      && scope != file_scope
+	      && scope != external_scope)
 	    {
 	      error ("nested function %q+D declared but never defined", p);
 	      undef_nested_function = true;