merge build_vs2012.bat into build.bat

Choose compiler with VS2012 and VS2010 switches.
Defaults to VS2010 if omitted.

Merge based on build_vs2012.bat and gccbuild.bat by XhmikosR
Merge pull request #39 from m0vie/scripts
Merge branch 'master' of https://github.com/mpc-hc/mpc-hc into master-dev
update contrib/icl13.diff