firebase-ios-sdk

Ordered code fixes (#2968)

* Fix endianness detection in OrderedCode

(and prevent further regression.)

* Use static_assert for constant checks

* Add a benchmark for SkipToNextSpecialByte

* Move string_apple_benchmark next to string_apple_test

* Accept non-const references in benchmark functions

This is a port of cl/132348268.

* Adjust Xcode project

* Add GoogleBenchmark as a dependency