This doesn't test much with gccgo, but at least it builds now, and the
test does, unsurprisingly, pass. A proper test would require adding
assembly files in GCC syntax for all platforms that gccgo supports,
which would be infeasible.
Also added copyright headers to the asm files.
Change-Id: Icea5af29d7d521a0681506ddb617a79705b76d33
Reviewed-on: https://go-review.googlesource.com/9417 Reviewed-by: Minux Ma <minux@golang.org>