Further C++ compatibility changes

src/xml.c

@@ -729,7 +729,7 @@ struct xml_document* xml_open_document(FILE* source) {
 /**
  * [PUBLIC API]
  */
-void xml_document_free(struct xml_document* document, _Bool free_buffer) {
+void xml_document_free(struct xml_document* document, bool free_buffer) {
 	xml_node_free(document->root);
 
 	if (free_buffer) {

src/xml.h

@@ -29,6 +29,7 @@
  */
 #include <stdint.h>
 #include <string.h>
+#include <stdbool.h>
 
 #ifdef __cplusplus
 extern "C" {
@@ -86,7 +87,7 @@ struct xml_document* xml_open_document(FILE* source);
  * @param free_buffer iff true the internal buffer supplied via xml_parse_buffer
  *     will be freed with the `free` system call
  */
-void xml_document_free(struct xml_document* document, _Bool free_buffer);
+void xml_document_free(struct xml_document* document, bool free_buffer);
 
 
 /**