fixed #172260 redundant assignment. fixed xmlSAXParseDoc() and

* SAX.c: fixed #172260 redundant assignment.
* parser.c include/libxml/parser.h: fixed xmlSAXParseDoc() and
  xmlParseDoc() signatures #172257.
Daniel
diff --git a/parser.c b/parser.c
index 990d2c6..c349282 100644
--- a/parser.c
+++ b/parser.c
@@ -12212,7 +12212,7 @@
  */
 
 xmlDocPtr
-xmlSAXParseDoc(xmlSAXHandlerPtr sax, xmlChar *cur, int recovery) {
+xmlSAXParseDoc(xmlSAXHandlerPtr sax, const xmlChar *cur, int recovery) {
     xmlDocPtr ret;
     xmlParserCtxtPtr ctxt;
     xmlSAXHandlerPtr oldsax = NULL;
@@ -12253,7 +12253,7 @@
  */
 
 xmlDocPtr
-xmlParseDoc(xmlChar *cur) {
+xmlParseDoc(const xmlChar *cur) {
     return(xmlSAXParseDoc(NULL, cur, 0));
 }
 #endif /* LIBXML_SAX1_ENABLED */