Fix another small memory leak

There was an early return with no corresponding free for the malloc'ed
known_stem_values. Now valgrind 3.9 doesn't complain of any possible leaks
coming from the infinality patched libfreetype.so.
Merge pull request #38 from goddesse/freetype2-iu-dev

There was an early return with no corresponding free for the malloc'ed known_stem_values. Now valgrind 3.9 doesn't complain of any possible leaks coming from the infinality patched libfreetype.so.