Fixed uninitialized variable use.

need_clip was introduced for fix #7
Merge branch 'fix_7_fonts_are_rendered_in_wrong_place'
Fixed #35 - micro freezes every few seconds

Freezes were due to the next music buffer generation. On iPad 2 it takes about 50 ms - to much.
I've moved music generation in the separate thread. This thread wakes up only if there are empty buffer to be filled. Main thread performs only song loading.
Code for music testing
Debug functions which I've used to measure whole frame time and time of different functions during the frame
helgrind suppression file

Helgrind shows only possible races inside SDL. It seems, that if I have
problems in my code, then they are not so obvious.
Forgotten header
Some debug utilities.
Fixed #36 - unsafe spikes

Now spikes behave like in an original game. And last cave should be little bit easier now.
New fixed numbers are based on the measurement, how much original game allows to intersect with the spikes.
Fixed #24 - Wrong collision detection

Enabled repel up. See description of the problemes in the commentary and in the issue description.