osdep/timer*: change license to LGPL

All authors have agreed, with the following exceptions:

e68d7f6858: wight wasn't asked (I think...), but even if he modified the
patch he applied, all code added by it was removed again later.

cb7768f9bb: nick could not be reached, but the declarations he added as
well as the full timer.c file were deleted again in cff81fe498 and
f800a42e45 (did it really take 6 years to remove unused declarations?).

ffaf4af230: it looks like this person wasn't contacted, but the code
added was removed again in f544bcf105.