Fix one place where semicolons were not recognized and fix the
pattern match for the syntax of some pseudo ops.
Also clean up a couple of unreachable code pieces.

There is still an undiagnosed bit difference betwen old and new .6
files. TBD.

With these fixes, asm can successfully compile and test the entire tree.
(Verified by
	turn off verifyAsm in cmd/go
	make.bash
	cp $GOROOT/bin/asm $GOROOT/pkg/tool/darwin_amd64/6a
	go test -short std
)

Change-Id: I91ea892098f76ef4f129fd2530e0c63ffd8745a9
Reviewed-on: https://go-review.googlesource.com/3688Reviewed-by: Russ Cox <rsc@golang.org>