Update NEWS and UPGRADING for zlib flock() support

[ci skip]

Closes phpGH-17752.

Author: ndossche

NEWS

@@ -165,6 +165,7 @@ PHP                                                                        NEWS
     is now a boolean. (David Carlier)
   . Fixed bug GH-16883 (gzopen() does not use the default stream context when
     opening HTTP URLs). (nielsdos)
+  . Implemented GH-17668 (zlib streams should support locking). (nielsdos)
 
 
 <<< NOTE: Insert NEWS from last stable release here prior to actual release! >>>

UPGRADING

@@ -107,6 +107,10 @@ PHP 8.5 UPGRADE NOTES
     and is not a QName because in those cases the namespace is taken
     from the namespace href or prefix respectively.
 
+- Zlib:
+  . flock() is now supported on zlib streams. Previously, this always
+    failed to perform any locking action.
+
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 3. Changes in SAPI modules
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