Ticket #3241: colon was not recognized inside escape seq in prompt.

export PS1=$'\[\e[38:5:214m\]orange$\[\e[0m\]'
mc

Expected: "orange$" prompt shows up in black under the panels.
Actual: some additional garbage.

The 256-color and true-color escape sequences should allow either ';' or
':' inside as separator, actually, ':' is the more correct according to
ECMA-48. Some terminal emulators (e.g. xterm, gnome-terminal) support
this.

Signed-off-by: Andrew Borodin <aborodin@vmail.ru>
Merge branch '3241_colon_in_prompt'

* 3241_colon_in_prompt:
  Ticket #3241: colon was not recognized inside escape seq in prompt.