Include .extern and .hidden in x86-64 asm.

It's unclear why .extern was being suppressed, it's also a little
unclear how the Chromium build was working without this. None the less,
it's causing problems with Android and it's more obviously correct to
make these symbols as hidden.

Change-Id: Id13ec238b80b8bd08d8ae923ac659835450e77f8
Reviewed-on: https://boringssl-review.googlesource.com/3800
Reviewed-by: Adam Langley <agl@google.com>
1 file changed