Changeset 359 for soft/giet_vm/giet_boot/boot.S

1/ Introduce the boot.S file that is the entry point
in the GIET-VM bootloader: The GIET-VM does not use
the preloader stack anymore, but uses its own stack
2/ Remove the seg_boot_buffer segment for the boot-loader.
The buffer used to load a complete .elf segment is defined
as a global variable in the seg_boot_data segment.
The GIET_ELF_BUFFER_SIZE is defined in the giet_config.h file.