Don't treat link-time warnings as errors when linking with libbusybox

See http://review.cyanogenmod.org/#/c/46642/ for why this is necessary.

Change-Id: Ib97484755569fcafc062d3c39b2841581987ca72
Fix roots.c to use fs_mgr

Change-Id: Ie68daba5e014dff0c4998da85576f35abe8ad270
move key loading to verifier code

Add an option to verifier_test to load keys from a file, the way the
recovery does.

Conflicts:
	verifier_test.c

Change-Id: Icba0e391164f2c1a9fefeab4b0bcb878e91d17b4
recovery: save logs from the last few invocations of recovery

Extends the last_log mechanism to save logs from the last six
invocations of recovery, so that we're more likely to have useful logs
even if the device has repeatedly booted into recovery.

Conflicts:
	recovery.c

Change-Id: I08ae7a09553ada45f9e0733fe1e55e5a22efd9f9
Merge branch 'cm-10.2' of https://github.com/CyanogenMod/android_bootable_recovery into HEAD