name-lookup.c (check_extern_c_conflict): Use DECL_SOURCE_LOCATION.

name-lookup.c (check_extern_c_conflict): Use DECL_SOURCE_LOCATION.

/cp
2019-09-25  Paolo Carlini  <paolo.carlini@oracle.com>

	* name-lookup.c (check_extern_c_conflict): Use DECL_SOURCE_LOCATION.
	(check_local_shadow): Use it in three additional places.

/testsuite
2019-09-25  Paolo Carlini  <paolo.carlini@oracle.com>

	* g++.dg/diagnostic/redeclaration-1.C: New.
	* g++.dg/lookup/extern-c-hidden.C: Test location(s) too.
	* g++.dg/lookup/extern-c-redecl.C: Likewise.
	* g++.dg/lookup/extern-c-redecl6.C: Likewise.
	* g++.old-deja/g++.other/using9.C: Likewise.

From-SVN: r276119