shift bug in constant evaluator

R=ken
OCL=18031
CL=18031

test/bugs/bug114.go

+// $G $D/$F.go && $L $F.$A && (./$A.out || echo BUG: bug114 failed)
+
+// Copyright 2009 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package main
+
+const B32 = 1<<32 - 1
+const C32 = (-1) & ((1<<32) - 1)
+const D32 = ^0
+
+func main() {
+	if B32 != 0xFFFFFFFF {
+		panicln("1<<32 - 1 is", B32, "should be", 0xFFFFFFFF)
+	}
+	if C32 != 0xFFFFFFFF {
+		panicln("(-1) & ((1<<32) - 1) is", C32, "should be", 0xFFFFFFFF)
+	}
+	if D32 != -1 {
+		panicln("^0 is", D32, "should be", -1)
+	}
+}