syscall: record argument size for all assembly functions

While we're here, fix Syscall9 on NetBSD and OpenBSD:
it was storing the results into the wrong memory locations.
I guess no one uses that function's results on those systems.

Part of cleaning up stack traces and argument frame information.

R=golang-dev, dvyukov
CC=golang-dev
https://golang.org/cl/11355044
15 files changed