Introduce an x86 interrupt stack frame that contains more information
than the non-debug one, namely the caller-saved GPRs, as well as an API
to retrieve it. Able to handle nested interrupts stack frames.
Change-Id: If182aaa2f34e4714b16ca65ff79da63b72d962f7
Signed-off-by: Benjamin Walsh <benjamin.walsh@windriver.com>