Problem Statement
=========
Fix various issues when building MySQL with Visual Studio 2015.

Fix:
=======
- Visual Studio 2015 adds support for timespec. Add check and
  related code to use this and only use our replacement if
  timespec is not defined.
- Rename lfind/lsearch to my* to avoid redefinition problems.
- Set default value for TMPDIR to "" on Windows as P_tmpdir
  no longer exists.
- using VS definition of snprintf if available
- tzname are now renamed to _tzname.