kernel: add mingw

Add the option to build a cross-compiler for kernel type 'mingw'.
The resulting cross-compiler can be used to build applications on a Linux host
that can be run on a Windows target.

Compiler is build using the mingwrt and w32-api packages aviable from the
MinGW project (http://sourceforge.net/projects/mingw).

The windows headers (w32-api package) are extracting with the kernel_headers
step The libraries and other headers from both packages are build and
installed in the various steps of libc

Signed-off-by: Bart vdr Meulen <bartvdrmeulen@gmail.com>
[yann.morin.1998@anciens.enib.fr: fix kernel headers comment, don't "return 0"]
Signed-off-by: "Yann E. MORIN" <yann.morin.1998@anciens.enib.fr>

 #!/bin/sh

 # this wrapper will not work under BSD systems or others

 # not containig the GNU readlink.

 # Under those, wrapper.c will forcibly be used

 # regardless of the config file setting.

 canonicalizedname=$(readlink -nm "${0}")

 dirname="$(dirname "${canonicalizedname}")"

 basename="$(basename "${canonicalizedname}")"

 ld_lib_path="$(dirname "${dirname}")/lib"

 case ":${LD_LIBRARY_PATH}:" in

     *":${ld_lib_path}:"*)   ;;

     *)  LD_LIBRARY_PATH="${ld_lib_path}${LD_LIBRARY_PATH:+:${LD_LIBRARY_PATH}}";;

 esac

 export LD_LIBRARY_PATH

 exec "${dirname}/.${basename}" "$@"