Fix compilation on ARM with android gcc 4.7

With the current code it fails due to running out
of registers.
So code the store offsets manually into the assembler
instead.
Passes "make fate-dts".

Signed-off-by: Reimar Döffinger <Reimar.Doeffinger@gmx.de>
Add thread-safe wrapper for get_format().

Just like get_buffer, get_format should not be called from a different
thread if thread_safe_callbacks is not set.

Signed-off-by: Reimar Döffinger <Reimar.Doeffinger@gmx.de>
sws: remove forgotten FAST_BGR2YV12 define

Signed-off-by: Michael Niedermayer <michaelni@gmx.at>