Add x[it][!] support to ex-command for VI mode.
Add x[it][!] support to ex-command for VI mode.

This requests adds the :x or :xit command to VI mode.
It does the same thing as :wq except it only writes
when changes have been made.

snmsts/lem,cxxxr/lem,cxxxr/lem,cxxxr/lem,snmsts/lem,cxxxr/lem,snmsts/lem,snmsts/lem