This is the convention that most classes stick to. The likely reason
why Dialog didn't stick to the convention was to be able to provide
a default value for this argument, but that feature wasn't very useful
since every caller already had access to the default surface.
The constructors of those classes now accept a string to be wrapped, instead
of a vector to be modified with split lines inserted into its middle.
Along with this conversion, manuals for applications stored in OPK packages
are now transferred into a string without garbage at the end.
In well-described fonts, this enables multi-line text (e.g. in manuals) to be
more readable.
The term "height" is also replaced with "line spacing" in Font's code.
Originally the font implementation was based on SFont, but it was
recently replaced by an SDL_ttf based implementation, so the name
no longer made sense.
Instead of having the copy constructor convert to display format, the new
copy constructor preserves the pixel format and a separate method was
introduced to convert surfaces to display format.
The code was made more robust as well: it should no longer crash if the
wallpaper cannot be loaded.
