Make julia-char-regex stricter.

This gives us more accurate highlighting, and makes julia-in-char more
accurate. Previously, it could be confused by:

                edit_insert(s, ';|')
            end
        end,
        '?' => function (s,o...)

because ; is legal before a character, and we weren't enforcing a
maximum length of character literals.

contrib/julia-mode.el

@@ -117,7 +117,7 @@ This function provides equivalent functionality, but makes no efforts to optimis
  (syntax whitespace)
  bol))
  (submatch "'"
- (or (*? (not (any "'"))) (not (any "\\"))
+ (or (repeat 0 7 (not (any "'"))) (not (any "\\"))
  "\\\\")
  "'")))