Add support for a third color in face definition that controls
the underline and a 'c' attribute for curly underline (that takes
precedence over 'u' if both are specified)
Allow empty colors to mean default, so that `,,red+u` means the
same as `default,default,red+u`
Fixes#4138
Ranges specified with a +<length> were inconsistent, with +0 meaning
an empty range, while +1 meant a two character long range (first character
+ the following one). Change that to mean a single character.
Fixes#3479
Using <fg>,<bg>+<attr>@<base> will apply the given fg color,
bg color and attributes on top of base dynamically. Simply giving
<base> is a shorthand for default,default@<base>.
Inspired by the discussion in #2862
That means we can now have highlighters active at global, buffer, and
window scope. The add-highlighter and remove-highlighter syntax changed
to take the parent path (scope/group/...) as a mandatory argument,
superseeding the previous -group switch.
Support arbitrary orders for column highlighters (it was previously
failing when column highlighters were not applied in column order).
Fix show_matching tab handling at the same time (horizontal scrolling,
tab characters and show_matching were behaving badly).
Window highlighting now runs user highlighters, then built-ins for each
phases, instead of running all phases for user highlighters, then all
phases for built-ins.
We now consider unprintable character to be 1-column width as we know
we will display them as "�".
Fixes#1615Fixes#1023
Instead of highlighting full lines and then trim them to make them
fit in the window, highlight only the visible portion, and rely on
the compute_display_setup system introduced for wrapping to setup
our buffer range correctly
Client quitting no longer immediately unwinds, client is just pushed
for deletion until we get back to the main loop, similarly to what
happens for buffer and window deletion.
