build: Added Visual Studio 2013 (VC12) project files

Carrying on from commit 11025613b9 added VC12 project files which are
capable of supporting side-by-side compilation, 32-bit and 64-bit
builds as well as support for some of the third-party libraries curl
uses.

projects/Windows/VC12/lib/.gitignore

@@ -0,0 +1,6 @@
+/*.vcxproj
+/*.filters
+/*.user
+/*.ncb
+/*.sdf
+/*.suo