Remove confusing _SELF macro.  Fix up memory handling for the expand method.
Remove confusing _SELF macro.  Fix up memory handling for the expand method.

sferik/libxml-ruby,sferik/libxml-ruby,increments/libxml-ruby,xml4r/libxml-ruby,increments/libxml-ruby,sferik/libxml-ruby,increments/libxml-ruby,xml4r/libxml-ruby,xml4r/libxml-ruby,sferik/libxml-ruby,sferik/libxml-ruby,sferik/libxml-ruby