findres: Unify with setres.

Unify setres and findres. setres uses XMETHOD to figure out the
best way to resize the display: cvt on XMETHOD != criat.

On XMETHOD=criat, try exact resolution (patched xorg-dummy), or
best approximation.
croutonfindnacl: Replace ifs by &&
Indentation fixes.
background.js: Registering windows event in a better place.
window.js: Simplify hide logic.