counters: add counters for DNS resolution.
examples: use fopen() for stream in mongoc-dump.
examples: remove some debug code.
gridfs: add mongoc_gridfs_file_remove() helper.
collection: remove spurious check for NULL index options.

Fixes CDRIVER-388
bulk: add option to change write_concern after creating structure.
matcher: fix some inconsistencies in matcher logic.
build: bump libbson
bindings: add language bindings prototypes.
php: use begin/end variants for building documents.
php: use inline hash iter api when checking for key type.
php: remove dead code.