This removes the emptyLayoutMod method from the LayoutModifier class, and
change the Stack parameter to redoLayout to a Maybe Stack one. It also changes
all affected code. This should should be a refactoring without any change in
program behaviour.
- printStringXMF: use the background color for XFT fonts too
- textWidthXMF now returns the text width even with xft fonts
- textExtentsXMF will now return only the ascend and the descent of a
string.
- stringPosition now takes the display too
- add support for UTF-8 locales: if the contrib library is compiled
with the 'with_xft' or the 'with_utf8' option the prompt and the
decoration system will support UTF-8 locales - this requires
utf8-strings.
