PHP-769: Test suite function for generating collection names
MongoWriteBatch::__construct() type validation test

This also touches up the exception message and adds the invalid value to it.
Merge pull request #590
Remove shadow declarations in collection.c
Remove declaration and assignment of unused variable
Merge pull request #592
PHP-993: Merge return array of individual batches into one array
Fix zts build
Attempt#2 to modify the batch statistics according to the spec