Related bnc#822625: Cache minimum height for table cells.

Change-Id: I35e295347a046376289f5d4fd5468860d0b8f0ae
Related bnc#822625: Cache FontEntry with the original FontSelectPattern.

Otherwise we never hit cache directly, only after expensive call to
ImplFindByFont.

Change-Id: If15b368feeba94c8fff8ee7cbe049fc4a2069768