pangoLayoutSetMarkupWithAccel(object, markup, accel.marker)objectmarkupaccel.markeraccel.charNULLaccel.marker is nonzero, the given character will mark the
character following it as an accelerator. For example, accel.marker
might be an ampersand or underscore. All characters marked
as an accelerator will receive a PANGO_UNDERLINE_LOW attribute,
and the first character so marked will be returned in accel.char.
Two accel.marker characters following each other produce a single
literal accel.marker character.