[MINOR] use 'is_set' instead of 'isset' in struct poller

'isset' was defined as a macro in /usr/include/sys/param.h, and
it breaks build on at least OpenBSD.
diff --git a/include/proto/fd.h b/include/proto/fd.h
index be52612..9b4c632 100644
--- a/include/proto/fd.h
+++ b/include/proto/fd.h
@@ -53,7 +53,7 @@
 
 #define EV_FD_SET(fd, ev)    (cur_poller.set((fd), (ev)))
 #define EV_FD_CLR(fd, ev)    (cur_poller.clr((fd), (ev)))
-#define EV_FD_ISSET(fd, ev)  (cur_poller.isset((fd), (ev)))
+#define EV_FD_ISSET(fd, ev)  (cur_poller.is_set((fd), (ev)))
 #define EV_FD_COND_S(fd, ev) (cur_poller.cond_s((fd), (ev)))
 #define EV_FD_COND_C(fd, ev) (cur_poller.cond_c((fd), (ev)))
 #define EV_FD_REM(fd)        (cur_poller.rem(fd))
diff --git a/include/types/fd.h b/include/types/fd.h
index 2128cb9..68335c0 100644
--- a/include/types/fd.h
+++ b/include/types/fd.h
@@ -2,7 +2,7 @@
   include/types/fd.h
   File descriptors states.
 
-  Copyright (C) 2000-2006 Willy Tarreau - w@1wt.eu
+  Copyright (C) 2000-2007 Willy Tarreau - w@1wt.eu
   
   This library is free software; you can redistribute it and/or
   modify it under the terms of the GNU Lesser General Public
@@ -73,7 +73,7 @@
  */
 struct poller {
 	void   *private;                                     /* any private data for the poller */
-	REGPRM2 int   (*isset)(const int fd, int dir);       /* check if <fd> is being polled for dir <dir> */
+	REGPRM2 int  (*is_set)(const int fd, int dir);       /* check if <fd> is being polled for dir <dir> */
 	REGPRM2 int     (*set)(const int fd, int dir);       /* set   polling on <fd> for <dir> */
 	REGPRM2 int     (*clr)(const int fd, int dir);       /* clear polling on <fd> for <dir> */
 	REGPRM2 int  (*cond_s)(const int fd, int dir);       /* set   polling on <fd> for <dir> if unset */