decl.c (grokdeclarator): Use locations[ds_storage_class] in error messages about ill-formed uses of mutable.

/cp
2019-01-16  Paolo Carlini  <paolo.carlini@oracle.com>

	* decl.c (grokdeclarator): Use locations[ds_storage_class] in
	error messages about ill-formed uses of mutable.

/testsuite
2019-01-16  Paolo Carlini  <paolo.carlini@oracle.com>

	* g++.dg/other/pr33558.C: Test location too.
	* g++.dg/other/pr33558-2.C: Likewise.
	* g++.dg/parse/crash4.C: Likewise.
	* g++.old-deja/g++.brendan/err-msg11.C: Likewise.
	* g++.old-deja/g++.mike/p7635.C: Likewise.
	* g++.old-deja/g++.other/decl6.C: Likewise.

From-SVN: r267978