Improve performance of multibyte utils.

Switch from using String#match to using String#=~. There's no need to
generate a MatchData for each iteration since we're not using it.
Signed-off-by: NJeremy Kemper <jeremy@bitsweat.net>

activesupport/lib/active_support/multibyte/utils.rb

@@ -27,7 +27,7 @@ def self.verify(string)
       def self.verify(string)
         if expression = valid_character
           # Splits the string on character boundaries, which are determined based on $KCODE.
-          string.split(//).all? { |c| expression.match(c) }
+          string.split(//).all? { |c| expression =~ c }
         else
           true
         end