Next batch of C++ to C comment style changes. Also improve and factor out endianness pre-processor code.

git-svn-id: https://llvm.org/svn/llvm-project/compiler-rt/trunk@78226 91177308-0d34-0410-b5e6-96231b3b80d8
diff --git a/lib/mulvti3.c b/lib/mulvti3.c
index 82efe8c..080cd63 100644
--- a/lib/mulvti3.c
+++ b/lib/mulvti3.c
@@ -1,24 +1,25 @@
-//===-- mulvti3.c - Implement __mulvti3 -----------------------------------===//
-//
-//                     The LLVM Compiler Infrastructure
-//
-// This file is distributed under the University of Illinois Open Source
-// License. See LICENSE.TXT for details.
-//
-//===----------------------------------------------------------------------===//
-//
-// This file implements __mulvti3 for the compiler_rt library.
-//
-//===----------------------------------------------------------------------===//
+/* ===-- mulvti3.c - Implement __mulvti3 -----------------------------------===
+ *
+ *                     The LLVM Compiler Infrastructure
+ *
+ * This file is distributed under the University of Illinois Open Source
+ * License. See LICENSE.TXT for details.
+ *
+ * ===----------------------------------------------------------------------===
+ *
+ * This file implements __mulvti3 for the compiler_rt library.
+ *
+ * ===----------------------------------------------------------------------===
+ */
 
 #if __x86_64
 
 #include "int_lib.h"
 #include <stdlib.h>
 
-// Returns: a * b
+/* Returns: a * b */
 
-// Effects: aborts if a * b overflows
+/* Effects: aborts if a * b overflows */
 
 ti_int
 __mulvti3(ti_int a, ti_int b)