unpackbootimg: Add support for device trees

Change-Id: I340eed99d2274a2f4cbaf5a9f27726ff3a9302e5
adb: Fix backup fallback

 * Check for existence of binary first

Change-Id: I5c1884655ae031f51cb935221ae7870b016e259d
property_get: do argument checking.

Try to verify, at compile time, that the supplied
value buffer is large enough.

Change-Id: I91fa560d3ceff87609194269356ac634bdbf2ede
Don't use __attribute__(__error__)

__attribute(__error__) isn't supported on clang, and generates
compiler warnings. Use __errordecl instead, which does the right thing
for different compilers.

Change-Id: Ifb0797a5de703cc5b3c39dcd97bcfaf404f1cafa