Add `m4` program

[Tim-Sobolev]

I was using w64devkit to build GNU MP library recently.

To run configure script from cmd.exe were created scripts, based on comment. Scripts were placed to the w64devkit\bin directory:

prepare.sh

if [[ "$OSTYPE" == "msys" ]]; then
    echo "MSYS..."
else
    export PATH_SEPARATOR=';'
    export ac_executable_extensions='.exe'
fi
export build_alias="$(uname -m)-pc-mingw64"

if [ -f configure ]
then
    echo "Converting configure..."
    sed -i 's/func_convert_file_msys_to_w32/func_convert_file_noop/' configure
    ./configure $@
fi

prepare.cmd

sh %~dp0prepare.sh %*

However, I have to use m4 from old unxutils project.
It will be nice to have it available in the standart distribution packege.