Make signature verification fail closed

check_signature carried STATUS_SUCCESS out of calculate_sha256 into the
trusted-key loop and never reset it, so a loop that never ran returned
success and every module would load unverified. Safe today with one key
present, but a fork, a rebrand or a key rotation that empties the array
would silently disable module authentication -- and without any of the
logging PAWNIO_UNRESTRICTED prints. Seed it with STATUS_INVALID_SIGNATURE.

calculate_sha256 had the same shape: if BCryptGetProperty reported an
unexpected property length the entire hash block was skipped and its
STATUS_SUCCESS returned over an uninitialized stack buffer.