Avoid an 1 byte out-of-bounds read in ASN1_PRINTABLE_type()

Avoid an 1 byte out-of-bounds read in ASN1_PRINTABLE_type()

In case the input is not NUL terminated, the reversed check for length
and terminating NUL results in a one-byte overread. The documentation
says that the input should be a string, but in ASN.1 land you never
know...

Reported by Guido Vranken a while back

ok beck