Previously we had a thread per test; once the number exceeded circa 250,
test-libbson --threads failed on MIPS.

Also standardize parsing of "NaN" and fix CDRIVER-1978: standard output
of NaN and Infinity.

Fixes CDRIVER-1938, there is now a lossless format for int64.

For consistency with libmongoc.

CDRIVER-2065 Document bson_init_static limitation on copying

Before, bson_as_json or bson_as_extended_json could ignore an error it encountered in a nested document while traversing the BSON structure to write JSON output.

Begin implementing extended JSON spec: output $numberInt.

Ensure man pages are distributed and that sphinx cache files .buildinfo
and .doctrees are cleaned.