bzip2: Disable MSVC warnings in 3rd party code

In commit 35acaa90c5 (bzip2: Add compilation flags to disable warnings
in third-party code, 2020-02-24) we forgot to disable warnings for MSVC.

Utilities/cmbzip2/bzlib_private.h

@@ -32,7 +32,9 @@
 
 #include "bzlib.h"
 
-
+#if defined(_MSC_VER)
+# pragma warning(push,1)
+#endif
 
 /*-- General stuff. --*/