Don't make unsized objects into extern.

Don't make unsized objects into extern.

2018-08-15  Iain Sandoe <iain@sandoe.co.uk>

gcc/c:

        PR c/19315
        * c-decl.c (finish_decl): Don't add the 'extern' storage class to
        objects of unknown size.

gcc/testsuite:

        PR c/19315
        gcc.dg/graphite/pr82451.c: Make array 'a' an extern.
        gcc.dg/redecl-10.c: Expect warnings for the static vars with unknown
        size.

git-svn-id: svn+ssh://gcc.gnu.org/svn/gcc/trunk@263556 138bc75d-0d04-0410-961f-82ee72b054a4