build.bat: Fix default compiler in help screen.
LAVFilters/build_lavfilters.bat: use VS2012 by default.
contrib/astyle.ini: Remove obsolete directory.
Use an empty line after #pragma once directives.
Remove icl13.diff.
AboutDlg: "Compiler" was written with upper case for FFmpeg and lower case for MPC-HC when copying to clipboard, make it consistent.
Add sign support for the VSFilter installer.
Rename "MPC-HC" compiler to "Compiler".

The previous text was misleading after the LAVFilters addition since LAVFilters are built with the same compiler as MPC-HC is.
Optimize sign support for the VSFilter installer.