Added FPU support for ChibiOS/RT

When an enabled FPU is detected we now use an appropriate stacking.

Change-Id: I1b0f43ec22e1c55c4f10e2ffa97d4aaa77bca5ee
Signed-off-by: Christian Gudrian <christian.gudrian@gmx.de>
Reviewed-on: http://openocd.zylin.com/2354
Tested-by: jenkins
Reviewed-by: Spencer Oliver <spen@spen-soft.co.uk>
doc: flash: write_image writes only loadable sections

The code that takes only sections marked PT_LOAD is in
image_elf_read_headers in src/target/image.c

(Just trying to save some time for the next person with same question.)

Change-Id: I493c102c908fca2b7238276ddbbecbe8c7cd9a0a
Signed-off-by: Alexei Colin <ac@alexeicolin.com>
Reviewed-on: http://openocd.zylin.com/2348
Tested-by: jenkins
Reviewed-by: Spencer Oliver <spen@spen-soft.co.uk>