[libpng16] Removed contrib/timepng from default build; it does not build

on platforms that don't supply clock_gettime().

ANNOUNCE

@@ -1,4 +1,4 @@
-Libpng 1.6.22rc01 - May 14, 2016
+Libpng 1.6.22rc02 - May 16, 2016
 
 This is not intended to be a public release.  It will be replaced
 within a few weeks by a public version or by another test version.
@@ -8,20 +8,20 @@ Files available for download:
 Source files with LF line endings (for Unix/Linux) and with a
 "configure" script
 
-   1.6.22rc01.tar.xz (LZMA-compressed, recommended)
-   1.6.22rc01.tar.gz
+   1.6.22rc02.tar.xz (LZMA-compressed, recommended)
+   1.6.22rc02.tar.gz
 
 Source files with CRLF line endings (for Windows), without the
 "configure" script
 
-   lp1622r01.7z  (LZMA-compressed, recommended)
-   lp1622r01.zip
+   lp1622r02.7z  (LZMA-compressed, recommended)
+   lp1622r02.zip
 
 Other information:
 
-   1.6.22rc01-README.txt
-   1.6.22rc01-LICENSE.txt
-   libpng-1.6.22rc01-*.asc (armored detached GPG signatures)
+   1.6.22rc02-README.txt
+   1.6.22rc02-LICENSE.txt
+   libpng-1.6.22rc02-*.asc (armored detached GPG signatures)
 
 Changes since the last public release (1.6.21):
 
@@ -99,9 +99,13 @@ Version 1.6.22beta06 [May 5, 2016]
     Fixed CMAKE_C_FLAGS with multiple values when genout is compiled on MSVC,
     Fixed pnglibconf.c compilation on OS X including the sysroot path.
 
-Version 1.6.22rcp1 [May 14, 2016]
+Version 1.6.22rc01 [May 14, 2016]
   No changes.
 
+Version 1.6.22rc02 [May 16, 2016]
+  Removed contrib/timepng from default build; it does not build on platforms
+    that don't supply clock_gettime().
+
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