ASN.1 DER: Make INT32 / INT64 types read badly encoded LONG zeroes

The deprecated ASN.1 type LONG / ZLONG (incorrectly) produced zero
length INTEGER encoding for zeroes.  For the sake of backward
compatibility, we allow those to be read without fault when using the
replacement types INT32 / UINT32 / INT64 / UINT64.

Fixes #7134

Reviewed-by: Tim Hudson <tjh@openssl.org>
(Merged from https://github.com/openssl/openssl/pull/7144)