This change introduces a generic way to provide binary data in setopt
options, called BLOBs.
This change introduces these new setopts:
CURLOPT_ISSUERCERT_BLOB, CURLOPT_PROXY_SSLCERT_BLOB,
CURLOPT_PROXY_SSLKEY_BLOB, CURLOPT_SSLCERT_BLOB and CURLOPT_SSLKEY_BLOB.
Reviewed-by: Daniel Stenberg
Closes#5357
