Why?
Most users who pass the current selection to grep likely do not intend to pass
the selection as a regex input string.
This makes the grepcmd use an additional -F flag to perform literal-string
matching for the current selection. The -F flag seems to be the standard flag
for literal-string matching in every grep implementation I've found.
`x` is often criticized as hard to predict due to its slightly complex
behaviour of selecting next line if the current one is fully selected.
Change `x` to use the previous `<a-x>` behaviour, and change `<a-x>` to
trim to fully selected lines as `<a-X>` did.
Adapt existing indentation script to the new behaviour
-verbatim will disable argument parsing in evaluate-commands, making
it possible to forward a single command to a different context without
triggering a reparsing of the arguments.
Fixes -try-client support in grep.kak
Closes#3153
