Merge from current r294767,294769,295408

r294767: Parse command line arguments in loader.fi
r294769: Allow newlines to be treated as whitespace when parsing args
r295408: Implement -P command line option in for EFI booting.

Approved by: re@ (gjb@)

MFC r281169, r293724, r293796, r294029, r294041, r294058

MFC r281169 (by andrew):
Make global variabled only used in this file static

MFC r294058:
Make common boot file_loadraw name parameter const

MFC r294041:
Remove unused reg param from fdt_fixup_memory

MFC r293724:
Enable warnings in EFI boot code

MFC r293796:
Fix typo in libefi.c

MFC r294029:
Only build EFI components on supported compilers

Sponsored by: Multiplay

MFC 279950:
Enable bzipfs support in the EFI loader.
- Add bzipfs to the list of supported filesystems in the EFI loader.
- Increase the heap size allocated for the EFI loader from 2MB to 3MB.

MFC r271762: Switch to text mode in UEFI boot

The loader previously failed to display on MacBooks and other
systems where the UEFI firmware remained in graphics mode.

Submitted by: Rafael Espindola

Approved by: re

MFC 279950:
Enable bzipfs support in the EFI loader.
- Add bzipfs to the list of supported filesystems in the EFI loader.
- Increase the heap size allocated for the EFI loader from 2MB to 3MB.

MFC r271762: Switch to text mode in UEFI boot

The loader previously failed to display on MacBooks and other
systems where the UEFI firmware remained in graphics mode.

Submitted by: Rafael Espindola

Approved by: re