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/doc/APIchunk18.html b/doc/APIchunk18.html
index 21013fd..8bc0157 100644
--- a/doc/APIchunk18.html
+++ b/doc/APIchunk18.html
@@ -221,9 +221,9 @@
 <a href="html/libxml-xmlmemory.html#xmlCleanupMemory">xmlCleanupMemory</a><br />
 <a href="html/libxml-parser.html#xmlCleanupParser">xmlCleanupParser</a><br />
 <a href="html/libxml-threads.html#xmlCleanupThreads">xmlCleanupThreads</a><br />
+<a href="html/libxml-parser.html#xmlHasFeature">xmlHasFeature</a><br />
 <a href="html/libxml-threads.html#xmlInitThreads">xmlInitThreads</a><br />
 <a href="html/libxml-globals.html#xmlInitializeGlobalState">xmlInitializeGlobalState</a><br />
-<a href="html/libxml-threads.html#xmlIsThreadsEnabled">xmlIsThreadsEnabled</a><br />
 <a href="html/libxml-threads.html#xmlLockLibrary">xmlLockLibrary</a><br />
 <a href="html/libxml-xmlmodule.html#xmlModuleFree">xmlModuleFree</a><br />
 <a href="html/libxml-xmlmodule.html#xmlModuleOpen">xmlModuleOpen</a><br />