PHP-1272 et al: Add missing bson_encode() tests and fix segfaults

 * https://jira.mongodb.org/browse/PHP-1272
 * https://jira.mongodb.org/browse/PHP-1273
 * https://jira.mongodb.org/browse/PHP-1277
That seem slike a made up value though?
These don't have a value - only a key...
idk. guess it doesn't matter. you shouldn't be serializing scalars like this anyway