Made auth_key_t have and made protob.tcc use timing_sensitive_equals.
Removed two speculative RSI comments.
Added AuthKeyTest unit test for new equality comparisons of auth_key_t.
Made error messages be back to what they were before.
Merge branch 'v1.6.x' into sam_fix_other_thing

Conflicts:
	src/protob/protob.tcc