This fixes a bug with the libevent backend on 32-bit platforms:

  https://github.com/wingo/fibers/issues/86

diff --git a/extensions/libevent.c b/extensions/libevent.c
index 4f44de9..52c9d73 100644
--- a/extensions/libevent.c
+++ b/extensions/libevent.c
@@ -215,7 +215,8 @@ run_event_loop (void *p)
     microsec = -1;
   else if (data->timeout >= 0)
     {
-      microsec = data->timeout / time_units_per_microsec;
+      microsec = (time_units_per_microsec == 0)
+	? 0 : data->timeout / time_units_per_microsec;
       tv.tv_sec = 0;
       tv.tv_usec = microsec;
     }
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<tr><td><span title='2016-12-14 21:58:32 +0100'>2016-12-14</span></td><td><a href='/guix/commit/d3.v3.js?id=4d93f312f084c34a70cf7da3abe5f92a74d76861'>graph: Add d3js backend.</a><span class='msg-avail'>...<span class='msg-tooltip'>* d3.v3.js, graph.js: New files.
* Makefile.am (EXTRA_DIST): List them.
* guix/graph.scm (%d3js-backend): New variable.
(emit-d3js-prologue, emit-d3js-epilogue, emit-d3js-node,
emit-d3js-edge): New procedures.
(%graph-backends): Add %d3js-backend.
</span></span></td><td>Ricardo Wurmus</td></tr>