re PR c++/51 (g++ reports error for ISO C++ example)

re PR c++/51 (g++ reports error for ISO C++ example)

cp:
	PR g++/51
	* parse.y (frob_specs): Indicate it is a language linkage which
	contained the extern.
	* decl.c (grokdeclarator): Allow extern language linkage with
	other specifiers.
testsuite:
	* g++.dg/other/linkage1.C: New test.
	* g++.old-deja/g++.brendan/err-msg2.C: Alter to avoid two
	specifiers.

From-SVN: r47891