* minibuffer.el (completion-pcm-complete-word-inserts-delimiters):

* minibuffer.el (completion-pcm-complete-word-inserts-delimiters):
New custom variable.
(completion-pcm--string->pattern): Use it.
(completion-pcm--pattern->regex, completion-pcm--pattern->string):
Make it handle any symbol as `any'.
(completion-pcm--merge-completions): Extract common suffix for the new
`prefix' symbol as well.
(completion-substring--all-completions): Use the new `prefix' symbol.