$.find: added indexOf checking for jqmData selector to improve speed on non-jqm selectors

$.find always runs regexp on given selector string. The problem is, that some apps (and even some widgets) do more normal selector searching than :jqmData searching. 

I added checking for :jqmData keyword in selector by simple indexOf method, which is faster, not that it makes a huge difference, but still.

Please refer to the test on [http://jsperf.com/jquery-mobile-find-patch-performance-fix](http://jsperf.com/jquery-mobile-find-patch-performance-fix "http://jsperf.com/jquery-mobile-find-patch-performance-fix")

Note that the
```js
jqmSelector = ":jqmData",
jqmDataRE = /:jqmData\(([^)]*)\)/g;
```
duplication could be changed also