Use Regexp#match? instead of =~ for better performance

* Avoids a MatchData allocation.

Author: eregon

lib/pathname.rb

@@ -215,7 +215,7 @@ def initialize(path)
     path = path.__send__(TO_PATH) if path.respond_to? TO_PATH
     @path = path.dup
 
-    if /\0/ =~ @path
+    if /\0/.match?(@path)
       raise ArgumentError, "pathname contains \\0: #{@path.inspect}"
     end
   end