Fixed building and warnings on Arduino (16 bit platform). (#4197)

Building on Arduino fixed by conditional includes of cstdint and utility. In the Standard C++ for Arduino (port of uClibc++):
* cstdint is not present.
* utility is named utility.h.

Replaced size_t with uoffset_t for Verifier::max_tables_, max_depth_, depth_, and num_tables_ to ensure 32-bit values are used (and not 16-bit) - gave rise to a warning.