libavutil/arm/asm.S sets '.arch' depending on HAVE_ARMV5TE so that
assembling armv5te code will always succeed even if the default -march
flag does not support it. HAVE_ARMV5TE_EXTERNAL tests assembling code
with the default arch.
Fixes the missing symbol ff_prefetch_arm with --cpu= not including
armv5te.
CC: libav-stable@libav.org
Move some functions from dsputil. The idea is that videodsp contains
functions that are useful for a large and varied set of video decoders.
Currently, it contains emulated_edge_mc() and prefetch().
Signed-off-by: Luca Barbato <lu_zero@gentoo.org>