Handle EHOSTUNREACH in errno_to_stream_end_reason()

We used to not recognize it and returned END_STREAM_REASON_MISC.
Instead, return END_STREAM_REASON_INTERNAL.

changes/misc-reason

+  o Minor bugfixes:
+    - Exit nodes didn't recognize EHOSTUNREACH as a stream ending reason
+      and sent back misc. Bugfix on 0.1.0.1-rc; fixes bug 1793.

src/or/reasons.c

@@ -161,6 +161,7 @@ errno_to_stream_end_reason(int e)
     E_CASE(EACCES):
     S_CASE(ENOTCONN):
     S_CASE(ENETUNREACH):
+    E_CASE(EHOSTUNREACH):
       return END_STREAM_REASON_INTERNAL;
     S_CASE(ECONNREFUSED):
       return END_STREAM_REASON_CONNECTREFUSED;