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>

# Build script for m4

CT_M4_VERSION=1.4.13

do_companion_tools_m4_get() {

    CT_GetFile "m4-${CT_M4_VERSION}" \

               {ftp,http}://ftp.gnu.org/gnu/m4

}

do_companion_tools_m4_extract() {

    CT_Extract "m4-${CT_M4_VERSION}"

    CT_Patch "m4" "${CT_M4_VERSION}"

}

do_companion_tools_m4_build() {

    CT_DoStep EXTRA "Installing m4"

    mkdir -p "${CT_BUILD_DIR}/build-m4"

    CT_Pushd "${CT_BUILD_DIR}/build-m4"

    CT_DoExecLog ALL \

    "${CT_SRC_DIR}/m4-${CT_M4_VERSION}/configure" \

        --prefix="${CT_TOOLS_OVERIDE_DIR}"

    CT_DoExecLog ALL make

    CT_DoExecLog ALL make install

    CT_Popd

    CT_EndStep

}