Key mappings lost when reopening Quickfix window

[reinerh]

When the Quickfix window is closed (q oder :ccl) and reopened (:copen), Ag's key mappings are no longer available.
Perhaps a new command can be added that reopens the Quickfix window with the already available results and sets up the key mappings again?

[losingkeys]

I'm not sure if those mappings can be set per-buffer, but I'll check that. Another thing to note that is if you do something like:

let g:ag_qhandler="copen 20"
let g:ag_lhandler="lopen 20"

Then the quickfix/location list windows will open larger... but not when you do :copen, because those variables only change how :Ag commands work.

Maybe it would be good to have an :AgLastSearch or similar command that:

1. opens the quickfix/location list (depending on what was opened last? or should there be an :LAgLastSearch too?)
2. reapplies the mappings
3. Uses the handler variables so the window is the right size/in the right spot