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>