implement a break_strings method and use it in string argument handler

+/*
+ * Break x,y,z and x+y+z into an array. String only.
+ *
+ * @param $str
+ *   The string to parse.
+ * @param $handler
+ *   The handler object to use as a base.
+ *
+ * @return $handler
+ *   The new handler object.
+ */
+function views_break_phrase($str, &$handler) {

This looks like it changes the documentation on views_break_phrase() to what should be on views_break_phrase_string().

Needs a bit of a port for D7.

D7 may benefit more from providing the string break to CTools instead, as well as tests for both functions.

I think there was something missed. All arguments are validate in query() but there are invalid in title() because title() still uses the old views_break_phrase() method.