libpayload: Provide atol(), malloc.h

Change-Id: I807ca061115146a6851eef481eb881b279fba8e1
Signed-off-by: Patrick Georgi <patrick.georgi@secunet.com>
Reviewed-on: http://review.coreboot.org/86
Tested-by: build bot (Jenkins)
Reviewed-by: Stefan Reinauer <stefan.reinauer@coreboot.org>

payloads/libpayload/include/stdlib.h

@@ -120,6 +120,7 @@ void *memalign(size_t align, size_t size);
  */
 long int strtol(const char *s, char **nptr, int base);
 unsigned long int strtoul(const char *s, char **nptr, int base);
+long atol(const char *nptr);
 
 /** @} */