fix leak of xmlNodes when not linked to a document
fix leak of xmlNodes when not linked to a document

gagern/libxmljs,gagern/libxmljs,hildjj/libxmljs,hildjj/libxmljs,rc0x03/libxmljs,libxmljs/libxmljs,improvisio-software/libxmljs,Visya/libxmljs,rc0x03/libxmljs,Konsus/libxml,Visya/libxmljs,CodeFridge/libxmljs_mem,polotek/libxmljs,rchipka/libxmljs,rchipka/libxmljs,libxmljs/libxmljs,polotek/libxmljs,Konsus/libxml,sergeche/libxmljs,libxmljs/libxmljs,polotek/libxmljs,CodeFridge/libxmljs_mem,CodeFridge/libxmljs_mem,sergeche/libxmljs,improvisio-software/libxmljs,rc0x03/libxmljs,Konsus/libxml,improvisio-software/libxmljs,sergeche/libxmljs,rchipka/libxmljs,hildjj/libxmljs,Visya/libxmljs,gagern/libxmljs