* Migrate FSTServerTimetsampValue to FSTDelegateValue
* Make ServerTimestamp use FSTFieldValue for previous value
This makes it possible integrate the FSTServerTimestampValue changes
earlier.
This includes the new FIRFieldValue sentinels, the FSTUserDataConverter code to parse them into internal ArrayTransform operations for use in an FSTTransformMutation, and some sanity testing in FSTMutationTests.
I still need to implement FSTTransformMutation support for local application and serialization (and then integration tests).
* 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
Gil