Zlib: Remove extern "C" for declarations in bundled private namespace

modules/juce_core/zip/zlib/JUCE_CHANGES.txt

@@ -3,3 +3,7 @@
 Include guards were added to these files to support multiple inclusion in a
 unity-style build.
 
+# zlib.h
+
+`extern "C"` was removed to avoid symbol collisions when including multiple
+copies of zlib in the same project.

modules/juce_core/zip/zlib/zlib.h

@@ -34,7 +34,7 @@
 #include "zconf.h"
 
 #ifdef __cplusplus
-extern "C" {
+// extern "C" {
 #endif
 
 #define ZLIB_VERSION "1.3.1"
@@ -1932,7 +1932,7 @@ ZEXTERN int            ZEXPORTVA gzvprintf(gzFile file,
 #endif
 
 #ifdef __cplusplus
-}
+// }
 #endif
 
 #endif /* ZLIB_H */