Add buffer-focus parse condition option.
Add buffer-focus parse condition option.

This instructs ycmd to parse a file when it gets focus, but only if that
file has never been parsed.

phst/emacs-ycmd,ptrv/emacs-ycmd,ptrv/emacs-ycmd,abingham/emacs-ycmd,emacsmirror/ycmd,abingham/emacs-ycmd,abingham/emacs-ycmd,phst/emacs-ycmd,emacsmirror/ycmd,emacsmirror/ycmd,ptrv/emacs-ycmd,emacsmirror/ycmd,abingham/emacs-ycmd,phst/emacs-ycmd,phst/emacs-ycmd,emacsmirror/ycmd,abingham/emacs-ycmd,emacsmirror/ycmd,phst/emacs-ycmd,ptrv/emacs-ycmd,phst/emacs-ycmd,ptrv/emacs-ycmd,ptrv/emacs-ycmd,abingham/emacs-ycmd