x86: provide more C standard environment

There are some external libraries that are built within
coreboot's environment that expect a more common C standard
environment. That includes things like inttypes.h and UINTx_MAX
macros. This provides the minimal amount of #defines and files
to build vboot_reference.

Change-Id: I95b1f38368747af7b63eaca3650239bb8119bb13
Signed-off-by: Aaron Durbin <adurbin@chromium.org>
Reviewed-on: http://review.coreboot.org/2859
Tested-by: build bot (Jenkins)
Reviewed-by: Ronald G. Minnich <rminnich@gmail.com>

src/include/inttypes.h

@@ -0,0 +1,4 @@
+#ifndef INTTYPES_H
+#define INTTYPES_H
+#include <stdint.h>
+#endif /* INTTYPES_H */