xf86-video-fglrx: Update to 13.6 beta (workaround beta signature)

Update to a new driver, that is working again. This supports also new hardware without watermarks. Signature is overwritten.

Old urls are kept in place, which can be changed mid june when 13.6 stable will be released.

Dropped:
Level51 workaround - not needed anymore
Kernel patches - this driver builds with 3.9.x out of the box