Fix comment.

flag.go

diff --git a/flag.go b/flag.go
index 7cc2755..8f5e8e7 100644
--- a/flag.go
+++ b/flag.go
@@ -269,7 +269,7 @@
 	exitOnError   bool     // does the program exit if there's an error?
 	errorHandling ErrorHandling
 	output        io.Writer // nil means stderr; use out() accessor
-	interspersed  bool      // do not allow interspersed option/non-option args
+	interspersed  bool      // allow interspersed option/non-option args
 }
 
 // A Flag represents the state of a flag.