HTTP client: Work around the 'gets' method not being supported by SSL BIOs
It turned out that loading non-ASN.1 contents using the HTTP client
fails over TLS because SSL BIOs do not support the gets method.
This PR provides a workaround by using the less efficient BIO_get_line() function
in case BIO_gets() returns -2, which means that it is not supported by the BIO.
Reviewed-by: Tomas Mraz <tomas@openssl.org>
(Merged from https://github.com/openssl/openssl/pull/17317)