Fix highlighting atom which contains '@', '!', '?'

Author: syohex

elixir-mode.el

@@ -127,7 +127,7 @@
                     (or
                      (and
                       (any "a-z" "A-Z" "_" "\"" "'")
-                      (zero-or-more (any "a-z" "A-Z" "0-9" "_" "\"" "'")))
+                      (zero-or-more (any "a-z" "A-Z" "0-9" "_" "\"" "'" "!" "@" "?")))
                      (and "\"" (one-or-more (not (any "\""))) "\"")
                      (and "'" (one-or-more (not (any "'"))) "'"))))
       (builtin . ,(rx (or line-start (not (any ".")))