Fix compilation on systems with older compilers.

This patch fixes a build error with GCC 7.x which doesn't seem to accept
const int's as constants in macro initialization.

See: tpo/core/tor#40410

changes/ticket40410

+  o Minor bugfixes (compilation):
+    - Fix a compilation error when trying to build Tor with a compiler that
+      does not support expanding statitically initialized const values in
+      macro's. Fixes bug 40410; bugfix on 0.4.6.5.

src/feature/dirclient/dirclient.c

@@ -1873,8 +1873,7 @@ dir_client_decompress_response_body(char **bodyp, size_t *bodylenp,
   /* If we're pretty sure that we have a compressed directory, and
    * we didn't manage to uncompress it, then warn and bail. */
   if (!plausible && !new_body) {
-    const int LOG_INTERVAL = 3600;
-    static ratelim_t warning_limit = RATELIM_INIT(LOG_INTERVAL);
+    static ratelim_t warning_limit = RATELIM_INIT(60 * 60);
     log_fn_ratelim(&warning_limit, LOG_WARN, LD_HTTP,
            "Unable to decompress HTTP body (tried %s%s%s, on %s).",
            description1,