glw: Get rid of glw_set() vararg attribute setter
glw: Do layout as a specific class callback (instead of signal)

Also start working on conditional refresh
Add conditional rendering of UI

This makes Showtime only redraw UI if needed.

Currently only available on RPI and OSX and needs to be enabled in settings:dev
Make it possible to show/hide sysinfo from menu
search: Add missing prop refs
pool: Fix typo in POOL_BY_MMAP mode