ARM: 4-byte align start of all asm functions

Due to apprent bugs in the GNU assembler and/or linker, relocations
can be incorrectly processed if the alignment of a Thumb instruction
is changed in the output file compared to the input object.

This fixes crashes in h264 decoding with Thumb enabled. No effect in
ARM mode since everything is 4-byte aligned there.
Signed-off-by: Mans Rullgard <mans@mansr.com>

libavcodec/arm/asm.S

@@ -68,6 +68,7 @@ ELF     .size   \name, . - \name
         .purgem endfunc
     .endm
         .text
+        .align          2
     .if \export
         .global EXTERN_ASM\name
 EXTERN_ASM\name: