Log Message:
Update devel/libbson to 1.1.7.

Libbson 1.1.7
- Unchecked error in bson_utf8_escape_for_json caused unbounded memory
  growth and a crash.
- Nicer floating-point formatting in bson_as_json.
- Link error with CMake on Mac.

Libbson 1.1.5
- Fix link error "missing __sync_add_and_fetch_4" in GCC on i386 -
  the functions bson_atomic_int_add and bson_atomic_int64_add are
  now compiled and exported if needed in i386 mode
- Fix version check for GCC 5 and future versions of Clang
- Fix warnings and errors building on various platforms