The console has gained these escape codes:
 - Set color to any of 256 entries in the palette.
 - Set color to any 24-bit RGB value.
 - Inverse mode.
 - Bold mode.
 - Underline mode.
 - Move cursor to line N.
 - \a is now ignored.

The effectively unused ATTR_CHAR has been removed. Parsing of escape codes
has been improved. The graphical palette has been changed to the tango
colors, which makes Sortix look a bit differently. Some user-space programs
have been changed to use different colors that look better under the new
palette.

Remove const from methods that weren't really const and remove mutable
keyword workaround.