Performance decrease in lftp 3.5.11 using gnutls instead of OpenSSL

[nico]

Using lftp 3.5.11 with gnutls 1.4.4 (with nls and zlib support enabled):
lftp :~> get https://localhost/data
104857600 bytes transferidos en 37 segundos. (2.74M/s)

And 100% CPU use.

Using lftp 3.5.11 with OpenSSL 0.9.8d

lftp :~> get https://localhost/data
104857600 bytes transferidos en 3 segundos. (33.07M/s)