Add vcpkg support for MSVC builds

Add vcpkg support for MSVC builds

- This allows building against newer and up-to-date versions of
  required libraries. Vcpkg is a library manager and can be found here:
  https://github.com/microsoft/vcpkg
- Libraries are provided for 32-bit and 64-bit.
  Current versions of libraries are e.g.:
  cairo 1.16.0, expat 2.2.6, fontconfig 2.12.4, freetype 2.9.1,
  gettext 0.19, glib 2.52.3, libpng 1.6.37, pango 1.40.11, pcre 8.41,
  libxml2 2.9.9 and zlib 1.2.11
  Furthermore these libraries from vcpkg are regularly updated.
- Added information to WIN32-BUILD-TIPS.txt and win32/README concerning
  vcpkg
- Added win32/Makefile_vcpkg.msc for building using nmake