Bugfixes and code improvements.

Added convenience constructors to SMFancyTextElement class.
Removed _context ivar from SMFancyText.
Converted some magic numbers into consts.
Replaced checks for nil equality with not operator.
Replaced for loop in SMFancyText drawRect: with iterator.
Leading whitespace removal works again (with faster/more accurate
algorithm).
Replaced calls to strcmp() with xmlStrcmp().