git-gui: use a tristate to control the case mode in the searchbar
git-gui: use a tristate to control the case mode in the searchbar

The config is now called gui.search.case and can have the three values:
no/yes/smart. yes is the default.

It also resets the case detection in smart mode, when the entry field was
cleared by the use.

Signed-off-by: Bert Wesarg <0d62a3713d750bb3a7440aad892eb1fd24c11fa3@googlemail.com>
Signed-off-by: Pat Thoyts <fe43a83262eef1680511f524a1e74d43c633cffe@users.sourceforge.net>

destenson/git,destenson/git,destenson/git,destenson/git,destenson/git,destenson/git,destenson/git,destenson/git