possible encoding issues with libxml2 functions

Hi

Today I played with xml_recv function and with xml processing functions.

xml_recv function ensures correct encoding from document encoding to server
encoding. But the decl section holds original encoding info - that should
be obsolete after encoding. Sometimes we solve this issue by removing decl
section - see the xml_out function.

Sometimes we don't do it - lot of functions uses direct conversion from
xmltype to xmlChar. Wrong encoding in decl section can breaks libxml2
parser with error

ERROR:  could not parse XML document
DETAIL:  input conversion failed due to input error, bytes 0x88 0x3C 0x2F
0x72
line 1: switching encoding: encoder error

This error is not often - but it is hard to find it - because there is
small but important difference between printed XML and used XML.

There are possible two fixes

a) clean decl on input - the encoding info can be removed from decl part

b) use xml_out_internal everywhere before transformation to
xmlChar. pg_xmlCharStrndup can be good candidate.

Comments?

Regards

Pavel