Add a thread-properties API
(Based on proposal at https://sourceware.org/glibc/wiki/ThreadPropertiesAPI)

This includes API to:
 - locate static and dynamic TLS
 - register thread-exit and  dynamic TLS creation/destruction callbacks

Change-Id: Icd9d29a5b2f47495395645e19d3b2c96826f19c8
diff --git a/libc/libc.map.txt b/libc/libc.map.txt
index 10732a1..e35d1fb 100644
--- a/libc/libc.map.txt
+++ b/libc/libc.map.txt
@@ -1554,6 +1554,10 @@
   global:
     ffsl;
     ffsll;
+    __libc_get_static_tls_bounds;
+    __libc_register_thread_exit_callback;
+    __libc_iterate_dynamic_tls;
+    __libc_register_dynamic_tls_listeners;
 } LIBC_R;
 
 LIBC_PRIVATE {