[dev.cc] asm: fix handling of statics (data<>) and symbols

A typo limited the number of center-dot substitutions to one. Fixed.

With these changes, plus a recent fix to 6a, the are no differences,
down to the bit level, in object code for any assembly files in std
between asm and 6a. (Runtime has not been checked yet, but I
expect no errors.)

Change-Id: I0e8045b4414223d937e7f8919c8768860554b7d5
Reviewed-on: https://go-review.googlesource.com/3820
Reviewed-by: Russ Cox <rsc@golang.org>

src/cmd/asm/internal/lex/input.go

@@ -422,6 +422,10 @@ func (in *Input) line() {
 	if err != nil {
 		in.Error("unquoting #line file name: ", err)
 	}
+	tok = in.Stack.Next()
+	if tok != '\n' {
+		in.Error("unexpected token at end of #line: ", tok)
+	}
 	obj.Linklinehist(linkCtxt, histLine, file, line)
 	in.Stack.SetPos(line, file)
 }