[truetype] Recalculate the sfnt table checksum always.

* src/truetype/ttobjs.c (tt_get_sfnt_checksum): Recalculate
the sfnt table checksum even if non-zero value is writte in
the TrueType font header.  Some bad PDF generators write
wrong values.  For detail, see examples and benchmark tests
of the latency by recalculation:
http://lists.gnu.org/archive/html/freetype-devel/2011-04/msg00091.html
http://lists.gnu.org/archive/html/freetype-devel/2011-04/msg00096.html
2 files changed