why can't I load pgxml.sql

1. ./configure --with-libxml --with-libxslt
2. make&&make install (successful)
3. test=# \i /usr/local/pgsql/share/contrib/pgxml.sql

error appearance:
SET
psql:/usr/local/pgsql/share/contrib/pgxml.sql:10: ERROR: could not load
library "/usr/local/pgsql/lib/pgxml.so": /usr/lib/libxml2.so.2:
undefined symbol: gzopen64
psql:/usr/local/pgsql/share/contrib/pgxml.sql:15: ERROR: could not load
library "/usr/local/pgsql/lib/pgxml.so": /usr/lib/libxml2.so.2:
undefined symbol: gzopen64
psql:/usr/local/pgsql/share/contrib/pgxml.sql:19: ERROR: could not load
library "/usr/local/pgsql/lib/pgxml.so": /usr/lib/libxml2.so.2:
undefined symbol: gzopen64
psql:/usr/local/pgsql/share/contrib/pgxml.sql:23: ERROR: could not load
library "/usr/local/pgsql/lib/pgxml.so": /usr/lib/libxml2.so.2:
undefined symbol: gzopen64
psql:/usr/local/pgsql/share/contrib/pgxml.sql:27: ERROR: could not load
library "/usr/local/pgsql/lib/pgxml.so": /usr/lib/libxml2.so.2:
undefined symbol: gzopen64
psql:/usr/local/pgsql/share/contrib/pgxml.sql:31: ERROR: could not load
library "/usr/local/pgsql/lib/pgxml.so": /usr/lib/libxml2.so.2:
undefined symbol: gzopen64
psql:/usr/local/pgsql/share/contrib/pgxml.sql:35: ERROR: could not load
library "/usr/local/pgsql/lib/pgxml.so": /usr/lib/libxml2.so.2:
undefined symbol: gzopen64
psql:/usr/local/pgsql/share/contrib/pgxml.sql:41: ERROR: could not load
library "/usr/local/pgsql/lib/pgxml.so": /usr/lib/libxml2.so.2:
undefined symbol: gzopen64
psql:/usr/local/pgsql/share/contrib/pgxml.sql:46: ERROR: function
xpath_list(text, text, unknown) does not exist
LINE 2: AS 'SELECT xpath_list($1,$2,'','')'
^
提示: No function matches the given name and argument types. You might
need to add explicit type casts.
psql:/usr/local/pgsql/share/contrib/pgxml.sql:56: ERROR: function
xpath_nodeset(text, text, unknown, unknown) does not exist
LINE 3: AS 'SELECT xpath_nodeset($1,$2,'''','''')'
^
提示: No function matches the given name and argument types. You might
need to add explicit type casts.
psql:/usr/local/pgsql/share/contrib/pgxml.sql:62: ERROR: function
xpath_nodeset(text, text, unknown, text) does not exist
LINE 3: AS 'SELECT xpath_nodeset($1,$2,'''',$3)'
^
提示: No function matches the given name and argument types. You might
need to add explicit type casts.
psql:/usr/local/pgsql/share/contrib/pgxml.sql:69: ERROR: could not load
library "/usr/local/pgsql/lib/pgxml.so": /usr/lib/libxml2.so.2:
undefined symbol: gzopen64
psql:/usr/local/pgsql/share/contrib/pgxml.sql:79: ERROR: could not load
library "/usr/local/pgsql/lib/pgxml.so": /usr/lib/libxml2.so.2:
undefined symbol: gzopen64
psql:/usr/local/pgsql/share/contrib/pgxml.sql:86: ERROR: could not load
library "/usr/local/pgsql/lib/pgxml.so": /usr/lib/libxml2.so.2:
undefined symbol: gzopen64

thanks all.

regards.