libpayload: x86: Add support for catching processor exceptions.

This functionality is already available for ARM, so lets add it to x86 as
well. We'll want to be able to hook exceptions when running as a remote GDB
target.

Change-Id: I42f640b08eb9eb86a1bcab3c327f7780191a2eb5
Signed-off-by: Gabe Black <gabeblack@google.com>
Reviewed-on: https://chromium-review.googlesource.com/179601
Reviewed-by: Aaron Durbin <adurbin@chromium.org>
Tested-by: Gabe Black <gabeblack@chromium.org>
Commit-Queue: Gabe Black <gabeblack@chromium.org>
(cherry picked from commit 5b8cf0c9f70a7e14766a2b095e6739a8d6321a34)
Signed-off-by: Isaac Christensen <isaac.christensen@se-eng.com>
Reviewed-on: http://review.coreboot.org/6898
Tested-by: build bot (Jenkins)
Reviewed-by: Edward O'Callaghan <eocallaghan@alterapraxis.com>

payloads/libpayload/arch/x86/main.c

@@ -27,6 +27,7 @@
  * SUCH DAMAGE.
  */
 
+#include <exception.h>
 #include <libpayload.h>
 
 unsigned long loader_eax;  /**< The value of EAX passed from the loader */
@@ -54,6 +55,8 @@ void start_main(void)
 	console_init();
 #endif
 
+	exception_init();
+
 	/*
 	 * Any other system init that has to happen before the
 	 * user gets control goes here.