Follow up to r289732: Update comments in source files to reference .cpp files

Patch by Hansang Bae

llvm-svn: 289739
diff --git a/openmp/runtime/src/z_Windows_NT-586_util.cpp b/openmp/runtime/src/z_Windows_NT-586_util.cpp
index 3aeafae..d7697d5 100644
--- a/openmp/runtime/src/z_Windows_NT-586_util.cpp
+++ b/openmp/runtime/src/z_Windows_NT-586_util.cpp
@@ -1,5 +1,5 @@
 /*
- * z_Windows_NT-586_util.c -- platform specific routines.
+ * z_Windows_NT-586_util.cpp -- platform specific routines.
  */