log: move Ldate doc to general declaration

The Ldate doc refers to all the constants.

Note that I changed "Bits or'ed" to "Bits are or'ed".

Fixes #21810

Change-Id: I82a66b589689e29063a39aa6d56000e00a5ed150
Reviewed-on: https://go-review.googlesource.com/62671
Reviewed-by: Ian Lance Taylor <iant@golang.org>

src/log/log.go

@@ -24,16 +24,16 @@ import (
 )
 
 // These flags define which text to prefix to each log entry generated by the Logger.
+// Bits are or'ed together to control what's printed.
+// There is no control over the order they appear (the order listed
+// here) or the format they present (as described in the comments).
+// The prefix is followed by a colon only when Llongfile or Lshortfile
+// is specified.
+// For example, flags Ldate | Ltime (or LstdFlags) produce,
+//	2009/01/23 01:23:23 message
+// while flags Ldate | Ltime | Lmicroseconds | Llongfile produce,
+//	2009/01/23 01:23:23.123123 /a/b/c/d.go:23: message
 const (
-	// Bits or'ed together to control what's printed.
-	// There is no control over the order they appear (the order listed
-	// here) or the format they present (as described in the comments).
-	// The prefix is followed by a colon only when Llongfile or Lshortfile
-	// is specified.
-	// For example, flags Ldate | Ltime (or LstdFlags) produce,
-	//	2009/01/23 01:23:23 message
-	// while flags Ldate | Ltime | Lmicroseconds | Llongfile produce,
-	//	2009/01/23 01:23:23.123123 /a/b/c/d.go:23: message
 	Ldate         = 1 << iota     // the date in the local time zone: 2009/01/23
 	Ltime                         // the time in the local time zone: 01:23:23
 	Lmicroseconds                 // microsecond resolution: 01:23:23.123123.  assumes Ltime.