Select DRM by default of compiled without RandR and VidMode

Signed-off-by: Mattias Andrée <maandree@operamail.com>
smarter autoselection of method: check environment variables

Signed-off-by: Mattias Andrée <maandree@operamail.com>
Always use the feature of the last commit

Signed-off-by: Mattias Andrée <maandree@operamail.com>
Merge branch 'auto-method' into ma-new