- Unbroke MIPS support which got entirely lost since the upgrade from 2.4.1:
  now all ISAs should work (MIPS1 would need kernel emulation though, untested)
- Fixed host installation which was broken on all targets
- Updated source origin to github and related variables
- Kept mipseb patch exception and MIPS16:=0 exclusion (needed for BB and CC compilation)

Only tested on a ZyXEL NBG6716 router which is MIPS32 (MIPS74Kc), ar71xx target.

Signed-off-by: Guillaume Déflache <guillaume.deflache@ibwag.com>