Add fixme/todo target to build.py.

Will show a list of lines in sourcefiles that either contains the string TODO
or FIXME.

Example output:

    user@host:~/src/ol3 $ ./build.py fixme
      src/ol/source/xyzsource.js has 4 matches:
        #1         // FIXME add minZoom support
        #46        // FIXME use goog.nullFunction ?
        #59        // FIXME factor out common code
        #76        // FIXME we shouldn't need a typecast here

      src/ol/interaction/dragpaninteraction.js has 2 matches:
        #1         // FIXME works for View2D only
        #39        // FIXME works for View2D only
Merge pull request #154 from marcjansen/todo

Add fixme/todo target to build.py.
Test if browser supports Windows Pointer events
Direct all pointer events to js code (IE pointer events).

see: http://msdn.microsoft.com/en-us/library/ie/hh673557(v=vs.85).aspx