Add support for iso14755

We launch dmenu for getting a codepoint, then convert it and send it to
the terminal.

config.def.h

@@ -172,6 +172,7 @@ static Shortcut shortcuts[] = {
 	{ MODKEY|ShiftMask,     XK_C,           clipcopy,       {.i =  0} },
 	{ MODKEY|ShiftMask,     XK_V,           clippaste,      {.i =  0} },
 	{ MODKEY,               XK_Num_Lock,    numlock,        {.i =  0} },
+	{ MODKEY,               XK_Control_L,   iso14755,       {.i =  0} },
 };
 
 /*