Change version numbers to 1.2.5.2 and release dates

Also added "-motley" to ZLIB_VERSION in zlib.h, so that versions
in-between 1.2.5.1 and 1.2.5.2 that are pulled down from github
can be identified as such if bugs are reported on them.

contrib/pascal/zlibpas.pas

@@ -10,7 +10,7 @@ unit zlibpas;
 interface
 
 const
-  ZLIB_VERSION = '1.2.5.1';
+  ZLIB_VERSION = '1.2.5.2';
 
 type
   alloc_func = function(opaque: Pointer; items, size: Integer): Pointer;