inf-ruby-completions: Get rid of the last semicolon

Again, for debugger.
inf-ruby-completions: Pass _pry_ when it's defined

Should improve the completions in the current Pry context.
inf-ruby-prompt-format: Fix not to match single operator chars

Like "/".
inf-ruby-switch-from-compilation: Call `comint-output-filter` on current line

This colors the prompt and sets inf-ruby-at-top-level-prompt-p.
inf-ruby-prompt-format: Include whitespace after rdb prompt