testsuite: g++.dg: debug: fix test filenames

gcc/testsuite/ChangeLog:
	PR debug/15736
	PR debug/46240

	* g++.dg/debug/pr15736.cc: Move to...
	* g++.dg/debug/pr15736.C: ...here.
	* g++.dg/debug/pr46240.cc: Move to...
	* g++.dg/debug/pr46240.C: ...here.

diff --git a/gcc/testsuite/g++.dg/debug/pr15736.cc b/gcc/testsuite/g++.dg/debug/pr15736.C
similarity index 100%
rename from gcc/testsuite/g++.dg/debug/pr15736.cc
rename to gcc/testsuite/g++.dg/debug/pr15736.C

diff --git a/gcc/testsuite/g++.dg/debug/pr46240.cc b/gcc/testsuite/g++.dg/debug/pr46240.C
similarity index 100%
rename from gcc/testsuite/g++.dg/debug/pr46240.cc
rename to gcc/testsuite/g++.dg/debug/pr46240.C