[fidlc] Fix uint64 negative parsing

ParseNumericLiteral() uses strtoull() to parse unsigned numeric types.
strtoull() parses negative numbers with unsigned integer wraparound
rules instead of failing. For all <64-bit unsigned types, this still
failed properly, since the wraparound would overrun the upper limit of
the type, but for uint64, this would incorrectly succeed. This change
addresses this error case.

Test: Run new test cases.
Change-Id: I4b419865bcb3059a362685ee1ac8229ee8034844