[efi] Add EFI image format and basic runtime environment

We have EFI APIs for CPU I/O, PCI I/O, timers, console I/O, user
access and user memory allocation.

EFI executables are created using the vanilla GNU toolchain, with the
EXE header handcrafted in assembly and relocations generated by a
custom efilink utility.

src/arch/i386/include/bits/nap.h

@@ -8,5 +8,6 @@
  */
 
 #include <gpxe/bios_nap.h>
+#include <gpxe/efi/efix86_nap.h>
 
 #endif /* _BITS_MAP_H */

src/arch/i386/include/gpxe/efi/efix86_nap.h

@@ -0,0 +1,16 @@
+#ifndef _GPXE_EFIX86_NAP_H
+#define _GPXE_EFIX86_NAP_H
+
+/** @file
+ *
+ * EFI CPU sleeping
+ *
+ */
+
+#ifdef NAP_EFIX86
+#define NAP_PREFIX_efix86
+#else
+#define NAP_PREFIX_efix86 __efix86_
+#endif
+
+#endif /* _GPXE_EFIX86_NAP_H */