testsuite: rename 2 files.

gcc/testsuite/ChangeLog:

	* g++.dg/cpp0x/pr56868.cpp: Moved to...
	* g++.dg/cpp0x/pr56868.C: ...here.
	* gcc.dg/torture/pr57993-2.cpp: Moved to...
	* g++.dg/torture/pr57993-2.C: ...here.

diff --git a/gcc/testsuite/g++.dg/cpp0x/pr56868.cpp b/gcc/testsuite/g++.dg/cpp0x/pr56868.C
similarity index 100%
rename from gcc/testsuite/g++.dg/cpp0x/pr56868.cpp
rename to gcc/testsuite/g++.dg/cpp0x/pr56868.C

diff --git a/gcc/testsuite/gcc.dg/torture/pr57993-2.cpp b/gcc/testsuite/g++.dg/torture/pr57993-2.C
similarity index 100%
rename from gcc/testsuite/gcc.dg/torture/pr57993-2.cpp
rename to gcc/testsuite/g++.dg/torture/pr57993-2.C