Removes the wlroots dependency from the common code. To remove the
dependency on the header, the defines and log-level enum are copied
over.
This causes a redefine error if both the wlr and the sway log.h are
included.
Introduce the sway_log functions as equivalents of the wlr_log
functions. This is a first step to free clients from the wlroots
dependency and allows to use the sway source path for file path
stripping which should get nicer __FILE__ cleans.
_sway_assert is a variadic function which tries
to delegate to another variadic function. This
requires a vprintf-style variant of the delegate.
https://stackoverflow.com/a/150616
Replicates i3 option. Verbosity level given as command line argument
becomes default log level, and using 'debuglog toggle' switches back and
forth between default and debug (or L_ERROR and debug if default is also
L_DEBUG).
