cmd/compile: stop aligning string data

Makes godoc 10KB smaller.
For #6853.

Change-Id: Id54bd8c82cb2a1ba11d2d724e3107f73024b19d9
Reviewed-on: https://go-review.googlesource.com/19696
Run-TryBot: David Crawshaw <crawshaw@golang.org>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Brad Fitzpatrick <bradfitz@golang.org>

src/cmd/compile/internal/gc/obj.go

@@ -234,7 +234,6 @@ func stringsym(s string) (hdr, data *Sym) {
 	}
 
 	off = duint8(symdata, off, 0) // terminating NUL for runtime
-	off = (off + Widthptr - 1) &^ (Widthptr - 1) // round to pointer alignment
 	ggloblsym(symdata, int32(off), obj.DUPOK|obj.RODATA|obj.LOCAL)
 
 	return symhdr, symdata