fixing bug #112904: html output method escaped plus sign character in URI

* HTMLtree.c: fixing  bug #112904: html output method escaped
  plus sign character in URI attribute.
Daniel
diff --git a/HTMLtree.c b/HTMLtree.c
index 9a39255..1d2f6de 100644
--- a/HTMLtree.c
+++ b/HTMLtree.c
@@ -615,7 +615,7 @@
 
 		while (IS_BLANK(*tmp)) tmp++;
 
-		escaped = xmlURIEscapeStr(tmp, BAD_CAST"@/:=?;#%&,");
+		escaped = xmlURIEscapeStr(tmp, BAD_CAST"@/:=?;#%&,+");
 		if (escaped != NULL) {
 		    xmlBufferWriteQuotedString(buf->buffer, escaped);
 		    xmlFree(escaped);