Redo border calculations for \be and \blur
Redo border calculations for \be and \blur

The last commit related to this overdid it a bit -- in some cases,
with \be5, for example, edges were visible on the outlines.  Instead of
using a linear function to map \be applications to border enlargement
value, use a nonlinear function, a simple square root. This seems to
work a lot better, while keeping the enlargement small.
In addition, make it possible to use \be and \blur at the same time. \be
is applied first.

astiob/libass,mwgoldsmith/libass,Akemi/libass,asimonov-im/libass,richardpl/libass,mwgoldsmith/libass,mwgoldsmith/libass,tgoyne/libass,astiob/libass,tgoyne/libass,stps/libass,libass/libass,torque/libass,rhlee/libass,blinkseb/libass,torque/libass,Distrotech/libass,stps/libass,libass/libass,tgoyne/libass,Distrotech/libass,grigorig/libass,sanyaade-g2g-repos/libass,Akemi/libass,pigoz/libass-ct,richardpl/libass,xbmc/libass,Akemi/libass,blinkseb/libass,MrSmile/libass,rhlee/libass,asimonov-im/libass,pigoz/libass-ct,vault/libass,stps/libass,torque/libass,sanyaade-g2g-repos/libass,grigorig/libass,rhlee/libass,ShiftMediaProject/libass,Distrotech/libass,richardpl/libass,xbmc/libass,blinkseb/libass,vault/libass,pigoz/libass-ct,sanyaade-g2g-repos/libass,MrSmile/libass,ShiftMediaProject/libass