valgrind + bff, multiple failures, initialize ref counts to 0...

for boost::intrusive_ptr

==6595== Conditional jump or move depends on uninitialised value(s)
==6595==    at 0xB21664D: intrusive_ptr_release(FontCharMap*) (metric.hxx:226)
==6595==    by 0xB2172F6: boost::intrusive_ptr<FontCharMap>::~intrusive_ptr() (intrusive_ptr.hpp:97)
==6595==    by 0xB5AE196: FtFontInfo::GetFontCharMap() (gcach_ftyp.cxx:1287)

Change-Id: Iea5ab13b093945c840481f29bc626a16dcbc234b