Pixelflinger: Add AArch64 support to pixelflinger JIT.

See the comment-block at the top of Aarch64Assembler.cpp
for overview on how AArch64 support has been implemented

In addition, this commit contains
[x] AArch64 inline asm versions of gglmul series of
    functions and a new unit test bench to test the
    functions

[x] Assembly implementations of scanline_col32cb16blend
    and scanline_t32cb16blend for AArch64, with unit
    test bench

Change-Id: I915cded9e1d39d9a2a70bf8a0394b8a0064d1eb4
Signed-off-by: Ashok Bhat <ashok.bhat@arm.com>