avoid passing a char[] as snprintf first argument. implemented

* encoding.c parserInternals.c: avoid passing a char[] as snprintf
  first argument.
* threads.c include/libxml/threads.h: implemented xmlIsThreadsEnabled()
  based on Andrew W. Nosenko idea.
* doc/* elfgcchack.h: regenerated the API
Daniel
diff --git a/parserInternals.c b/parserInternals.c
index 6ec8d4b..f3fcd6f 100644
--- a/parserInternals.c
+++ b/parserInternals.c
@@ -728,7 +728,7 @@
     {
         char buffer[150];
 
-	snprintf(buffer, 149, "Bytes: 0x%02X 0x%02X 0x%02X 0x%02X\n",
+	snprintf(&buffer[0], 149, "Bytes: 0x%02X 0x%02X 0x%02X 0x%02X\n",
 			ctxt->input->cur[0], ctxt->input->cur[1],
 			ctxt->input->cur[2], ctxt->input->cur[3]);
 	__xmlErrEncoding(ctxt, XML_ERR_INVALID_CHAR,