qtutils: s/callback/fn/

Signed-off-by: David Aguilar <davvid@gmail.com>
qtutils: add connect_toggle()

For connecting checkboxes and similar widgets.
grep: refresh when the "shell" checkbox is clicked

Signed-off-by: David Aguilar <davvid@gmail.com>
grep: allow choosing the regular expression mode

Add a combo box for choosing the regular expression mode.

"git grep" supports three modes:

	--basic-regexp (POSIX basic regular expressions)
	--extended-regexp (POSIX extended regular expressions)
	--fixed-strings (search for fixed strings)

Expose these modes using a combo box next to the text input field.

Signed-off-by: David Aguilar <davvid@gmail.com>