Changes: Updates for release 3.21

Signed-off-by: Michael Kerrisk <mtk.manpages@gmail.com>

Changes

@@ -1,6 +1,6 @@
 ==================== Changes in man-pages-3.21 ====================
 
-Released: ????-??-??, Christchurch
+Released: ????-??-??, Los Gatos
 
 
 Contributors
@@ -9,6 +9,9 @@ Contributors
 The following people contributed notes, ideas, or patches that have
 been incorporated in changes in this release:
 
+Frank Dana <ferdnyc@gmail.com>
+Michael Kerrisk <mtk.manpages@gmail.com>
+Roman Byshko <rbyshko@gmail.com>
 
 Apologies if I missed anyone!
 
@@ -16,19 +19,46 @@ Apologies if I missed anyone!
 New and rewritten pages
 -----------------------
 
+pthread_setconcurrency.3
+    Michael Kerrisk
+        New page documenting pthread_setconcurrency(3) and
+	pthread_getconcurrency(3)
 
-Newly documented interfaces in existing pages
----------------------------------------------
+pthread_yield.3
+    Michael Kerrisk
+        New page documenting pthread_yield(3)
 
 
 New and changed links
 ---------------------
 
-
-Global changes
---------------
-
+pthread_getconcurrency.3
+    Michael Kerrisk
+	New link to new pthread_setconcurrency(3)
 
 Changes to individual pages
 ---------------------------
 
+initrd.4
+    Michael Kerrisk
+        Various minor wording improvements
+
+initrd.4
+    Frank Dana
+        Add missing word in description
+
+feature_test_macros.7
+    Michael Kerrisk
+        Update for glibc 2.10 changes to <features.h>
+            From glibc 2.10, <features.h> understands the values 200809
+            for _POSIX_C_SOURCE and 700 for _XOPEN_SOURCE, and makes
+            corresponding changes to defaults for other feature test macros.
+    Michael Kerrisk
+        Add an example program
+            This example program makes it possible to explore what
+            feature test macros are set depending on the glibc version
+            and the macros that are explicitly set.
+
+ldconfig.8
+    Michael Kerrisk
+        /etc/ld.so.conf also include libraries found in /lib and /usr/lib