build/Makefile-newvs.am: Update Comments for Usage
build/Makefile-newvs.am: Update Comments for Usage

Update the notes that this is also used for Visual Studio 2015 support,
and correct the MSVC_VER_LONG for MSVC 2015, which is 14, not 2015.

Also add a note that this can be used for other projects that have
Visual Studio build support.

Distrotech/pango,Distrotech/pango,Distrotech/pango