Hi All, 


This patch adds support for Semihosting v2 support for ARM
in libgloss.

Semihosting v2 changes are documented here:
https://developer.arm.com/docs/100863/latest/

The biggest change is the addition of an extensions mechanism
to add more extensions in the future.

Regression tested on aarch64-none-elf and no regressions.

OK for master?

PS. I don't have commmit rights so if OK can someone apply for me?

Thanks,
Tamar


libgloss/aarch64/
2017-07-03  Tamar Christina  <tamar.christina@arm.com>

	* _kill.c (_kill): Add exit code reporting.
	* _exit.c (_exit): Likewise.
	* svc.h (AngelSVC_Reason_IsError): New.
	(AngelSVC_Reason_ReportExceptionExtended): New.
	(AngelSVC_Reason_Elapsed, AngelSVC_Reason_TickFreq): New.
	(NUM_SHFB_MAGIC, SHFB_MAGIC_0, SHFB_MAGIC_2, SHFB_MAGIC_3): New.
	(SH_EXT_EXIT_EXTENDED_BITNUM, SH_EXT_STDOUT_STDERR_BITNUM): New.
	* syscalls.c (get_semihosting_exts, has_ext_exit_extended): New.
	(has_ext_stdout_stderr, initialise_semihosting_exts): New.
	(initialise_monitor_handles): Check for extension.