Feature: add a parametere to set the default underline color.
Usage: lemonbar -Ucolor
By the way this also fix a strange behavior whereas '%{+u}correct%{U-}strange'
made the second underline of the same color as the background instead of the foreground.
The before code would skip a percent sign even if it was not followed by a {}
block. The after code checks the same condition but only advances p if a {} block
is found and otherwise passes it through as text.
An error will not be printed if the parameter to `T` is not valid (- or
a number) and the token will be eaten (just like when an invalid
attribute is found)
Remove the ability of the -f switch to accept a comma-separated list of fonts. The user is expected
to use multiple times -f whenever he wants to specify one or more fonts. This has the side effect of
enabling the user to use fonts whose name contains a comma.
