do not explicitly refresh rnd state on session deinit

It is already being refreshed during the session lifetime.
doc update
doc update
doc update
_gnutls_dh_generate_key() will account the q_bits
When gnutls_global_init() is called manually from the application check the urandom fd for validity

That addresses the issue where a server closes all open file descriptors
and then calls gnutls_global_init().

Conflicts:
	lib/nettle/rnd-common.c
dropped gnutls_fd_in_use, it is no longer necessary

Conflicts:
	lib/libgnutls.map
updated text for gnutls_fd_in_use() to account the new behavior
doc update
corrected exit state from gnutls_global_init