Shuffled where various compatibility items of code are amongst the headers in msvc directory so:

  Not too many warnings are disabled in source file that includes spandsp.h

  A copy of the msvc/spandsp.h file to spandsp/src directory so project that uses it only needs to add one directory to search, or can even just explicitly put the path in for the spandsp.h file.

  Removal of need for windows.h to be implicitly included by user source file via spandsp.h, can cause conflicts.

  Some symbol conflicts with other libraries.

git-svn-id: http://svn.freeswitch.org/svn/freeswitch/trunk@12272 d0543943-73ff-0310-b7d9-9358b9ac24b2