Fix double-free in gnutls_pkcs12_simple_parse()
when exporting curve coordinates to X9.63 format, perform additional sanity checks on input

Reported by Sean Burford.
doc update
bumped version
updated testcompat
treat GNUTLS_E_GOT_APPLICATION_DATA as non-fatal if initial negotiation is complete

This corrects a regression introduced in b5a0de2e6da98866cafb770c3141b7353d030ab2
Reported by Dan Winship. https://savannah.gnu.org/support/?108690
doc update
_gnutls_x509_get_dn() always return a null terminated string