Fix  120Hz-reset issue on linux

This fixes #64 on linux.

Short summary: (see bugreport for full discussion)

LWGJL reads the monitor config at startup. On shutdown, this information is used to reset the configuration.
However, LWJGL did not remember/parse the frequencies of the screens. This resulted in default frequencies being applied on exit, thus resetting the frequency from 120Hz to default (60Hz).

This patch modifies the XRandR utility class to save and later apply the frequencies.
Also, the detection of the current mode was improved. (it now searches for the modeline with the star (*)).

These changes only affect quitting LWJGL-applications, so there should be no side effects.
I also verified the new parsing logic to work with all supported versions of xrandr. (1.2 and up, as it always was).