xinitrc: major refactoring putting more conditional code and tests.
xinitrc: major refactoring putting more conditional code and tests.

Not a major change in how it works, but a refactoring to let
conditionally execute more parts.
Also checking for presence of most of the programs used or called.
Initial code to check dynamically for 1 or 2 monitors and monitor
rotation. It is not working very well.

rff/cfgbin,rff/cfgbin,rff/cfgbin,rff/cfgbin