Match gccgo error messages.

bug090.go:41:6: error: floating point constant truncated to integer
bug090.go:32:6: error: floating point constant truncated to integer
bug090.go:34:14: error: floating point constant truncated to integer
bug090.go:37:5: error: incompatible types in assignment
bug090.go:40:5: error: incompatible types in assignment

R=rsc
DELTA=2  (0 added, 0 deleted, 2 changed)
OCL=26564
CL=26574

test/fixedbugs/bug090.go

@@ -38,9 +38,9 @@ func main() {
 	assert(i != f3div2, "i != f3div2");	// ERROR "truncate"
 
 	const g float64 = 1.0;
-	i = g;  // ERROR "convert"
+	i = g;  // ERROR "convert|incompatible"
 
 	const h float64 = 3.14;
-	i = h;  // ERROR "convert"
+	i = h;  // ERROR "convert|incompatible"
 	i = int(h);	// ERROR "truncate"
 }