#27 Fix warning in tclxml.c

[Daniel Collins]

Minor tweak to tcldom-libxml2.h to add in the public functions (Tcldom_libxml2_Init).
This fixed a minor warning in tclxml.c

../../../src/tclxml-3.2/tclxml.c: In function `Tclxml_Init':
../../../src/tclxml-3.2/tclxml.c:252: warning: implicit declaration of function `Tcldom_libxml2_Init'

This may not be the best place for the addition...

[Daniel Collins]