Second stage of adding support for 64-bit integral data types - this

Second stage of adding support for 64-bit integral data types - this
causes the configure script to attempt to define the PRI[doux]64 macros
if they're not defined by including <inttypes.h>, and causes
"missing/bittypes.h" to attempt to define them, if undefined, in a
fashion that should, with any luck, work on MSVC++ and various flavors
of GNU C on Windows.

Fix the spelling of "Mac OS X".