[style] Remove some stray tabs in C/C++ source files

Change-Id: I1aeb5465f419f4613da429c865db4a8e15a076cc

[bootloader] commandline processing overhaul

- maintain a single central commandline
- simplify interface to this commandline
- ensure that later additions to the commandline
correctly override same-named existing entries
- split legacy boot path into its own file
- bump bootloader version
- display bootloader version next to bootloader name
- disable some debug chatter, declutter things a bit

Change-Id: I86e10bddd156089582bcb079018e5bb780cbbf24

[gigaboot] initial support for "native" magenta boot

Change-Id: I3319b584c64153a789e88f66ea91f484c39d1873

[bootloader][xefi] Break load_file into two stages

xefi_open_file() will attempt to open a file
xefi_read_file() will read it into a buffer
xfei_load_file() combines the two

With this change, we can show a message before loading a (potentially
large) ramdisk.

Change-Id: I81c07570f6db08690ff1119823b8982b57b9e04d

[bootloader] utils.h becomes xefi.h, helper functions renamed

Change-Id: I395ce58f9272b4b6cea4dd9103acf1938737e2af

[bootloader] Initial import of gigaboot

Original source:
https://fuchsia.googlesource.com/gigaboot20x6/
Upstream commit:
80eef665f1e248eafe48f9b430fdae702ece20c1

Change-Id: I1be9ad20831e0d790937446febc28755943884a5