Added support for e-mail constraints.
Added gnutls_x509_name_constraints_check_crt

This function will check name constraints against all the names
in a certificate.
Verify name constraints.
simplify names
removed false warnings
certtool allows setting name constraints.
_gnutls_parse_general_name2() will return the expected data
properly indent name constraints
Added tool to create a certificate chain
If alternative names are found, don't bother checking the DN.
Added check for null
removed debugging
Allow empty names.
_gnutls_x509_read_value() can now read empty values.
pretty print empty DNSnames
Updated test for name constraints to include empty constraints names.
corrected empty name check
better error printing
Added tests for name constraints addition.
doc update