#103 Improvements for the vc_solution folder

[Michael Fink]

Here's a patch to update the Visual Studio README file and fix a few bugs in the VS build. I created the patch based on the latest revision r6572 as of today.

Changes:
improved README for Visual Studio
changed libsndfile .lib and .dll names to match modern libsndfile versions
converted sln solution files to the slnx format
added missing GTK1 include folders for mp3x tool

Cheers,
Michael

[Alexander Leidinger]

Committed (after adaption, I had a lot of changes there not yet committed). Thanks!