Fix for CF objects leak in MGMushParser.m:setBaseFont

In **MGBox2/MGBox/MGMushParser.m:setBaseFont**, `boldName` and a few other CF objects were leaking due to the extra retains created by `CTFontCopyName` and other functions. I confirmed the leak on my iPhone by creating mush multilines.

This patch releases the no longer needed objects using `CFRelease` at the end of `setBaseFont`'s execution.