Add the msys-core package

This is a plain conversion of msysrlsbld.ini which comes as part of
msysCORE-1.0.18-1-msys-1.0.18-src.tar.lzma with the only exception that
the debug files are neither built nor packaged.

Signed-off-by: Sebastian Schuberth <sschuberth@gmail.com>
msys-core: Apply patches from the msysgit project

These are the patches from

    https://github.com/msysgit/msysgit/tree/msys/src/rt/patches

with minor modifications so that they still apply. Note that

    0010-quote-paths-for-non-msys-programs-that-contain-wildc.patch

has been deleted as it has been applied upstream and

    0012-bash-Don-t-load-user32.dll-for-every-shell-process.patch

was removed because it patches bash, not the msys runtime.

Signed-off-by: Sebastian Schuberth <sschuberth@gmail.com>