(completion-table-with-context): Fix `pred' for the

(completion-table-with-context): Fix `pred' for the
various kinds of completion tables.
(completion-emacs22-try-completion): Place cursor after the /, as was
done in Emacs-22's minibuffer-complete-word.
Fix bug reported by David Hansen <david.hansen@gmx.net>.
(completion-emacs22-try-completion): Merge all mergable text rather than /.
(completion-pcm--delim-wild-regex): New var.
(completion-pcm-word-delimiters): New custom.
(completion-pcm--prepare-delim-re, completion-pcm--pattern-trivial-p)
(completion-pcm--string->pattern, completion-pcm--pattern->regex)
(completion-pcm--all-completions, completion-pcm-all-completions)
(completion-pcm--merge-completions, completion-pcm--pattern->string)
(completion-pcm-try-completion): New functions.
(completion-styles-alist): Add them.
(completion-styles): Add it to the default.