(iswitchb-single-match-face)

(iswitchb-single-match-face)
(iswitchb-current-match-face, iswitchb-virtual-matches-face)
(iswitchb-invalid-regexp-face): New faces.
(iswitchb-completions): Use them.
(iswitchb-use-faces): Renamed from iswitchb-use-fonts, which is
now marked as an obsolete alias.
(iswitchb-read-buffer): Remove check for bound font variables.
(iswitchb-invalid-regexp): New free variable.
(iswitchb-get-matched-buffers): Catch invalid-regexp errors and
set iswitchb-invalid-regexp.
(iswitchb, iswitchb-complete, iswitchb-completions): Deal with invalid regexps.
(iswitchb-completions): Add check for complete match when entering a regexp.
(iswitchb-completions): Remove require-match argument.
(iswitchb-exhibit): Fix caller.
(iswitchb-common-match-inserted): New variable.
(iswitchb-complete, iswitchb-completion-help): Use it.