When checking for data to be received use the 'transport_recv_ptr'

This affects cases where there is different send and recv pointers.
Reported and investigated by JMRecio.
doc update
eliminated the leak of hint when deallocating the credentials.
use custom proc_server_kx for RSA-PSK
Enable hint in the rsa-psk test.
doc update
updated gnulib
Avoid dual generation of key.
doc update