Remove own_window_argb_value setting, specify alpha directly in own_window_colour
Refactor range_config_setting
colour_traits: Clamp values of rgba components
Random improvements to the list_map class
synchronized() function: call a functor while holding a lock
Add get() to thread_handle
Use a recursive mutex for locking lua objects
Add support for scopes to table_layout

support in x11_output is still minimal - only changing of foreground colour is supported.
Add font-changing support to x11_scope
table_layout: don't forget to unref the state table
luamm: use references instead of pointers in callbacks

I do this to be more consistent with the idea "use references everywhere the object cannot be
null".
Fix a bug in destruction of data source objects
Introduce the nodename data source
Fix vertical alignment of xft fonts