Issue #18527: Upgrade internal copy of zlib to 1.2.8
diff --git a/Modules/zlib/compress.c b/Modules/zlib/compress.c
index ea4dfbe..6e97626 100644
--- a/Modules/zlib/compress.c
+++ b/Modules/zlib/compress.c
@@ -29,7 +29,7 @@
     z_stream stream;
     int err;
 
-    stream.next_in = (Bytef*)source;
+    stream.next_in = (z_const Bytef *)source;
     stream.avail_in = (uInt)sourceLen;
 #ifdef MAXSEG_64K
     /* Check for source > 64K on 16-bit machine: */