C++ compatibility for Windows compilation

C++ compatibility for Windows compilation

pull up r21902, r21917, r21918, r21919 to improve C++ compatibility
and to enable Windows compilation.

 ------------------------------------------------------------------------
 r21919 | raeburn | 2009-02-09 11:36:09 -0500 (Mon, 09 Feb 2009) | 3 lines

 Check C++ compatibility for some internal headers that may (now or in
 the future) be used in C++ code on Windows.
 ------------------------------------------------------------------------
 r21918 | raeburn | 2009-02-09 11:35:01 -0500 (Mon, 09 Feb 2009) | 3 lines

 More C++ compatibility: Don't use "typedef struct tag *tag"; rename
 the tag and keep the same typedefname.
 ------------------------------------------------------------------------
 r21917 | raeburn | 2009-02-09 11:28:29 -0500 (Mon, 09 Feb 2009) | 3 lines

 C++ compatibility fix -- g++ says "types may not be defined in casts",
 so do the gcc unaligned-struct trick only for C, not C++.
 ------------------------------------------------------------------------
 r21902 | raeburn | 2009-02-05 16:56:21 -0500 (Thu, 05 Feb 2009) | 2 lines

 use casts, for c++ compilation on windows

ticket: 6536
version_fixed: 1.7.1
target_version: 1.7.1
tags: pullup

git-svn-id: svn://anonsvn.mit.edu/krb5/branches/krb5-1-7@22455 dc483132-0cff-0310-8789-dd5450dbe970