Ongoing cleanups.

src/compress_zlib.cpp

@@ -211,7 +211,7 @@ int upx_zlib_test_overlap  ( const upx_bytep buf,
         return UPX_E_ERROR;
     // NOTE: there is a very tiny possibility that decompression has
     //   succeeded but the data is not restored correctly because of
-    //   in-place buffer overlapping.
+    //   in-place buffer overlapping, so we use an extra memcmp().
     if (tbuf != NULL && memcmp(tbuf, b, *dst_len) != 0)
         return UPX_E_ERROR;
     return UPX_E_OK;
@@ -236,10 +236,12 @@ const char *upx_zlib_version_string(void)
     return zlibVersion();
 }
 
+#if 0 /* UNUSED */
 unsigned upx_zlib_adler32(const void *buf, unsigned len, unsigned adler)
 {
     return adler32(adler, (const Bytef *) buf, len);
 }
+#endif
 
 #if 0 /* UNUSED */
 unsigned upx_zlib_crc32(const void *buf, unsigned len, unsigned crc)