Function node_get_content 

pub unsafe fn node_get_content(node: *mut _xmlNode) -> *mut xmlChar

Get the content of a node, recursively concatenating child text.

UPSTREAM-PARITY

xmlChar *xmlNodeGetContent(const xmlNode *cur);

Oracle behavior (tree.c xmlNodeGetContent):

• For text/CDATA nodes: returns the content directly.
• For element nodes: recursively concatenates the string values of children (text and CDATA; entity references are expanded via their content when available).
• For attribute nodes: returns the attribute value (first child).
• For comments/PIs: returns the content field.
• For documents: returns content of the root element.
• Returns NULL on error, empty string for empty nodes.

Returns a newly allocated string; caller frees with xmlFree.