Use S_CASE for ehostunreach, not E_CASE. Partial backport of 69deb22f. Fixes 0.2.1 compilation on windows

src/or/reasons.c

@@ -166,7 +166,7 @@ errno_to_stream_end_reason(int e)
     S_CASE(ENOTCONN):
     S_CASE(ENETUNREACH):
       return END_STREAM_REASON_INTERNAL;
-    E_CASE(EHOSTUNREACH):
+    S_CASE(EHOSTUNREACH):
       /* XXXX022
        * The correct behavior is END_STREAM_REASON_NOROUTE, but older
        * clients don't recognize it.  So we're going to continue sending