Backport: ruby-mode: Detect regexps after `!'

Fixes: debbugs:19285

* lisp/progmodes/ruby-mode.el (ruby-syntax-before-regexp-re): Detect
regexps after `!'.

(cherry picked from commit 8854b9cf)

lisp/ChangeLog

+2015-03-20  Dmitry Gutov  <dgutov@yandex.ru>
+
+	* progmodes/ruby-mode.el (ruby-syntax-before-regexp-re): Detect
+	regexps after `!'.  (Bug#19285)
+
 2015-03-20  Dmitry Gutov  <dgutov@yandex.ru>
 
 	* progmodes/ruby-mode.el (ruby-font-lock-keywords): Use

lisp/progmodes/ruby-mode.el

@@ -1777,7 +1777,7 @@ It will be properly highlighted even when the call omits parens.")
   (defvar ruby-syntax-before-regexp-re
     (concat
      ;; Special tokens that can't be followed by a division operator.
-     "\\(^\\|[[{|=(,~;<>]"
+     "\\(^\\|[[{|=(,~;<>!]"
      ;; Distinguish ternary operator tokens.
      ;; FIXME: They don't really have to be separated with spaces.
      "\\|[?:] "