Added a core description file for ARM Cortex-M4.
Added a basic file and config set to start porting for ARM STM32F4.

The linker script is just some picked from the STM firmware examples.
Updated target description. Now we are able to build all files wihtin stm32/* against the code sourcery arm toolchain.
I think this would be a great starting point to think about a proper memory map where and how the kernel is linked to asecure area.
Merge branch 'master' of https://github.com/thebaron06/retrobsd