Port of: https://github.com/firebase/firebase-js-sdk/pull/559
Should address #772 once released.
getNextMutationBatchAfterBatchId() was not respecting
highestAcknowledgedBatchId and therefore we were resending writes after the
network was disabled / re-enabled.
- FSTTimestamp is now FIRTimestamp, under Firestore/Source/{Public,API}. This is a temporary solution; eventually, FIRTimestamp is supposed to live somewhere under Firebase;
- move most internal Timestamp methods to the public header (the only exception is ISOString).
* Move all Firestore files to Objective-C++
* Update project file references
* Don't use module imports from Objective-C++
* Use extern "C" for C-accessible globals
* Work around more stringent type checking in Objective-C++
* NSMutableDictionary ivars aren't implicitly casted to NSDictionary
* FSTMaybeDocument callback can't be passed a function that accepts
FSTDocument
* NSComparisonResult can't be multiplied by -1 without casting
* Add a #include <inttypes.h> where needed
* Avoid using C++ keywords as variables
* Remove #if __cplusplus guards
Michael Lehenbauer