updated copyright notice in LICENSE file
same as before with dwm.c as well
applied Hiltjo's resize/move limitation

"Limit the amount of updates when resizing or moving a window in floating
mode to 60 times per second. This makes resizing and moving alot smoother
and by limiting it it also uses alot less resources on my machine.
Merge branch 'master' of git://git.suckless.org/dwm