Rename test .c sources to .cpp where necessary (#604)

Remove hacks to force language from CMake files.

Closes KhronosGroup/OpenCL-CTS#25

test_conformance/profiling/CMakeLists.txt

@@ -1,14 +1,14 @@
 set(MODULE_NAME PROFILING)
 
 set(${MODULE_NAME}_SOURCES
-    main.c
-    readArray.c
-    writeArray.c
-    readImage.c
-    writeImage.c
-    copy.c
-    execute.c
-    execute_multipass.c
+    main.cpp
+    readArray.cpp
+    writeArray.cpp
+    readImage.cpp
+    writeImage.cpp
+    copy.cpp
+    execute.cpp
+    execute_multipass.cpp
 )
 
 include(../CMakeCommon.txt)