This commit ensures that a fully constructed Font object will not crash
gmenu2x when it is used, even if loading the font or initialising SDL_ttf
altogether has failed. Instead, it will render no text, but icons and
images are still drawn.
The proper way to signal an error would be to throw an exception and fail
to construct the Font object. However, gmenu2x does not use exceptions.
Since 2002-09-03, SDL_ttf performs reference counting on TTF_Init and
TTF_Quit. If two fonts were loaded concurrently via the Font class and
one was destructed, the destructor of the first object would call TTF_Quit,
making the second object unusable. The constructor now calls TTF_Init
unconditionally to prevent this situation.
The reference counting behavior was introduced in this SDL_ttf commit:
http://hg.libsdl.org/SDL_ttf/rev/fc0371908009
Replaced Font constructor with factory method, so that if the TTF
cannot be loaded, the Font object is not constructed. The normal C++
way of handling this is with exceptions, but we're compiling with
-fno-exceptions.
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.
