Log Message:
Update devel/libbson 1.1.10 to 1.2.0.

libbson 1.2.0
- Add bson_mem_restore_vtable(), the inverse of bson_mem_set_vtable().
- Enable runtime asserts in release build.
- Fixed compiler warnings and build failures on various platforms.
- Improvements to the formatting and contents of the documentation.

libbson 1.1.11
- Document bson streaming reads with an example, bson-streaming-reader.c.
- Document callback function types bson_reader_destroy_func_t and
  bson_reader_read_func_t.