Function xmlTextReaderQuoteChar 

#[unsafe(no_mangle)]
pub unsafe extern "C" fn xmlTextReaderQuoteChar(
    reader: *mut XmlTextReader,
) -> c_int

int xmlTextReaderQuoteChar(xmlTextReaderPtr reader).

UPSTREAM-PARITY: libxml2 2.13/2.15 returns '"' unconditionally for any non-NULL reader (the implementation is a placeholder that does not inspect the attribute; see the /* TODO maybe lookup the attribute value */ comment in xmlreader.c). The candidate reproduces that historical behavior exactly.