fix handling of floating point zero constant 0p+0

R=r
DELTA=25  (25 added, 0 deleted, 0 changed)
OCL=29875
CL=29875

src/cmd/gc/lex.c

@@ -807,6 +807,9 @@ tnum:
 		}
 	}
 
+	if(c == 'p')	// 0p begins floating point zero
+		goto casep;
+
 	c1 = 0;
 	for(;;) {
 		if(!isdigit(c))

test/fixedbugs/bug160.dir/x.go

+// 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 x
+
+const Zero = 0.0
+const Ten = 10.0

test/fixedbugs/bug160.dir/y.go

+// 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
+
+import "os"
+import "x"
+
+func main() {
+	if x.Zero != 0 {
+		println("x.Zero = ", x.Zero);
+		os.Exit(1);
+	}
+	if x.Ten != 10 {
+		println("x.Ten = ", x.Ten);
+		os.Exit(1);
+	}
+}

test/fixedbugs/bug160.go

+// $G $D/bug160.dir/x.go && $G $D/bug160.dir/y.go && $L y.$A x.$A && ./$A.out
+
+// 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.
+
+nothing to see here