check for stdnoreturn.h presence
alpn: fix version documentation

Signed-off-by: Nikos Mavrogiannopoulos <nmav@gnutls.org>
updated included libtasn1
when importing a certificate, keep the DER data

Conflicts:
	lib/x509/verify.c
when importing a CRL keep the DER data
avoid new allocations and keep a pointer to the DER data for DN

Conflicts:
	lib/x509/crl.c
	lib/x509/x509.c
corrected bundled vasprintf(); reported by Jeff Lee
steal openconnect's vasprintf() implementation
when setting a DN properly handle spaces and escaped commas
doc update
optimized escaped comma handling
gnutls_x509_crl_verify: do not always set the invalid status

Reported by Armin Burgmeier.
Revert "gnutls_x509_crl_verify: do not always set the invalid status"

This reverts commit d29a0027fd554ee1aa92c186c6040f53f15cdab7.
gnutls_x509_crl_verify: do not always set the invalid status

Reported by Armin Burgmeier.
doc update
doc update
bumped version
Merge tag 'tags/gnutls_3_2_18'

released 3.2.18