Various updates that came from rhel 7.1 work.
- Clean up the build a bit to make it faster
- Make grubenv work right on UEFI machines
- Sort debug and rescue kernels later than normal ones
- Allow "fallback" to include entries by title as well as number.
- Fix a segfault on aarch64.
- Load arm with SB enabled if available.
- Add some serial port options to GRUB_MODULES.
Signed-off-by: Peter Jones <email@example.com>