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/powitf2.c b/lib/powitf2.c
index 34aa2cb..3dacbf6 100644
--- a/lib/powitf2.c
+++ b/lib/powitf2.c
@@ -1,21 +1,22 @@
-//===-- powitf2.cpp - Implement __powitf2 ---------------------------------===//
-//
-//                     The LLVM Compiler Infrastructure
-//
-// This file is distributed under the University of Illinois Open Source
-// License. See LICENSE.TXT for details.
-//
-//===----------------------------------------------------------------------===//
-//
-// This file implements __powitf2 for the compiler_rt library.
-//
-//===----------------------------------------------------------------------===//
+/* ===-- powitf2.cpp - Implement __powitf2 ---------------------------------===
+ *
+ *                     The LLVM Compiler Infrastructure
+ *
+ * This file is distributed under the University of Illinois Open Source
+ * License. See LICENSE.TXT for details.
+ *
+ * ===----------------------------------------------------------------------===
+ *
+ * This file implements __powitf2 for the compiler_rt library.
+ *
+ * ===----------------------------------------------------------------------===
+ */
 
 #if _ARCH_PPC
 
 #include "int_lib.h"
 
-// Returns: a ^ b
+/* Returns: a ^ b */
 
 long double
 __powitf2(long double a, si_int b)