[gnutls-devel] Doc improvements

[Attila Molnar]

Hello everyone,

Two doc patches follow; the first one is obvious.
The second tries to clarify a grey area about the SRP server callback.
Previously it was unclear what to do with the already allocated data
that was put into the datum structures provided by gnutls if a failure
happened in a later step (deallocate+clear it or leave it there?).

Regards, Attila