Add newer m4 required by bison from git-for-windows/sdk

Signed-off-by: Thomas Braun <thomas.braun@byte-physics.de>
Add precompiled bison 2.4.1

Downloaded from http://sourceforge.net/projects/mingw/files/MSYS/Extension/bison/bison-2.4.1-1/bison-2.4.1-1-msys-1.0.11-bin.tar.lzma/download and extracted.

Signed-off-by: Thomas Braun <thomas.braun@byte-physics.de>
Change release script to involve less fancy logic

Signed-off-by: Thomas Braun <thomas.braun@byte-physics.de>
Add patch files for all bash patch releases

Signed-off-by: Thomas Braun <thomas.braun@byte-physics.de>
Updated bash.exe/sh.exe to 3.1.20(4)

Bring bash from patchlevel 0 to patchlevel 20.

This update fixes the following security bugs:
- CVE-2014-6271
- CVE-2014-7169
- CVE-2014-7186
- CVE-2014-7187

Signed-off-by: Thomas Braun <thomas.braun@byte-physics.de>
Merge pull request #254 from t-b/tb_add_newer_bash

Update bash to patch release 20