libpayload: Add an exec() and i386_do_exec() function

Add functions for libpayload to execute other payloads in memory,
and have those functions return cleanly.

Signed-off-by: Jordan Crouse <jordan.crouse@amd.com>
Acked-by: Uwe Hermann <uwe@hermann-uwe.de>


git-svn-id: svn://svn.coreboot.org/coreboot/trunk@3338 2b7e53f0-3cfb-0310-b3e9-8179ed1497e1

payloads/libpayload/libc/Makefile.inc

@@ -29,4 +29,4 @@
 
 TARGETS-y += libc/malloc.o libc/printf.o libc/console.o libc/string.o
 TARGETS-y += libc/memory.o libc/ctype.o libc/ipchecksum.o libc/lib.o
-TARGETS-y += libc/rand.o libc/time.o libc/lar.o
+TARGETS-y += libc/rand.o libc/time.o libc/lar.o libc/exec.o