updated the docs and rebuild releasing 2.6.21 removed

* NEWS elfgcchack.h testapi.c doc/*: updated the docs and rebuild
  releasing 2.6.21
* include/libxml/threads.h threads.c: removed xmlIsThreadsEnabled()
* threads.c include/libxml/threads.h xmllint.c: added the more
  generic xmlHasFeature() as suggested by Bjorn Reese, xmllint uses it.
Daniel
diff --git a/elfgcchack.h b/elfgcchack.h
index eef3f9a..44ab139 100644
--- a/elfgcchack.h
+++ b/elfgcchack.h
@@ -4071,6 +4071,16 @@
 #endif
 #endif
 
+#ifdef bottom_parser
+#undef xmlHasFeature
+extern __typeof (xmlHasFeature) xmlHasFeature __attribute((alias("xmlHasFeature__internal_alias")));
+#else
+#ifndef xmlHasFeature
+extern __typeof (xmlHasFeature) xmlHasFeature__internal_alias __attribute((visibility("hidden")));
+#define xmlHasFeature xmlHasFeature__internal_alias
+#endif
+#endif
+
 #ifdef bottom_tree
 #undef xmlHasNsProp
 extern __typeof (xmlHasNsProp) xmlHasNsProp __attribute((alias("xmlHasNsProp__internal_alias")));
@@ -4695,16 +4705,6 @@
 #endif
 #endif
 
-#ifdef bottom_threads
-#undef xmlIsThreadsEnabled
-extern __typeof (xmlIsThreadsEnabled) xmlIsThreadsEnabled __attribute((alias("xmlIsThreadsEnabled__internal_alias")));
-#else
-#ifndef xmlIsThreadsEnabled
-extern __typeof (xmlIsThreadsEnabled) xmlIsThreadsEnabled__internal_alias __attribute((visibility("hidden")));
-#define xmlIsThreadsEnabled xmlIsThreadsEnabled__internal_alias
-#endif
-#endif
-
 #ifdef bottom_xmlsave
 #undef xmlIsXHTML
 extern __typeof (xmlIsXHTML) xmlIsXHTML __attribute((alias("xmlIsXHTML__internal_alias")));
@@ -7649,6 +7649,18 @@
 
 #if defined(LIBXML_PATTERN_ENABLED)
 #ifdef bottom_pattern
+#undef xmlPatternMinDepth
+extern __typeof (xmlPatternMinDepth) xmlPatternMinDepth __attribute((alias("xmlPatternMinDepth__internal_alias")));
+#else
+#ifndef xmlPatternMinDepth
+extern __typeof (xmlPatternMinDepth) xmlPatternMinDepth__internal_alias __attribute((visibility("hidden")));
+#define xmlPatternMinDepth xmlPatternMinDepth__internal_alias
+#endif
+#endif
+#endif
+
+#if defined(LIBXML_PATTERN_ENABLED)
+#ifdef bottom_pattern
 #undef xmlPatternStreamable
 extern __typeof (xmlPatternStreamable) xmlPatternStreamable __attribute((alias("xmlPatternStreamable__internal_alias")));
 #else