testsuite: rename files in c-c++-common.

gcc/testsuite/ChangeLog:

	* c-c++-common/Walloca-larger-than.C: Moved to...
	* c-c++-common/Walloca-larger-than.c: ...here.

diff --git a/gcc/testsuite/c-c++-common/Walloca-larger-than.C b/gcc/testsuite/c-c++-common/Walloca-larger-than.c
similarity index 100%
rename from gcc/testsuite/c-c++-common/Walloca-larger-than.C
rename to gcc/testsuite/c-c++-common/Walloca-larger-than.c