git-gui: Add a menu of available encodings.

To make encoding selection easier, add a menu that
lists available encodings to the Options window.

Menu structure is borrowed from Firefox.

Signed-off-by: Alexander Gavrilov <angavrilov@gmail.com>
Tested-by: Johannes Sixt <johannes.sixt@telecom.at>
Signed-off-by: Shawn O. Pearce <spearce@spearce.org>
2 files changed