[MINOR] add support for the polling results in fdtab

Now fdtab can contain the FD_POLL_* events so that the pollers
which can fill them can give userful information to readers and
writers about the precise condition of wakeup.
diff --git a/src/proxy.c b/src/proxy.c
index 93eab16..9096c91 100644
--- a/src/proxy.c
+++ b/src/proxy.c
@@ -153,6 +153,7 @@
 			fdtab[fd].cb[DIR_RD].b = fdtab[fd].cb[DIR_WR].b = NULL;
 			fdtab[fd].owner = (struct task *)curproxy; /* reference the proxy instead of a task */
 			fdtab[fd].state = FD_STLISTEN;
+			fdtab[fd].ev = 0;
 			listeners++;
 		}