Tweak test to work with both 6g and gccgo.

Pull the struct into a single line, since 6g reports the error
on the last line of the struct definition and gccgo reports it
on the first line.

6g:
bug215.go:12: invalid recursive type A

gccgo:
bug215.go:12:6: error: invalid recursive type ‘A’

R=rsc
https://golang.org/cl/180044

test/fixedbugs/bug215.go

@@ -9,8 +9,6 @@
 
 package main
 
-type A struct {
+type A struct {	a A }	// ERROR "recursive"
-	a A;
-}			// ERROR "recursive"
 func foo()		{ new(A).bar() }
 func (a A) bar()	{}