Fix broken epoll detection. Add the write only fd of the pipe to the epoll set and check if the fd is ready for writing. The earlier test works with older linux distros but fails with newer ones.

This commit was SVN r20945.

config/ompi_setup_libevent.m4

@@ -210,8 +210,9 @@ AC_INCLUDES_DEFAULT
     memset(&epevout, 0, sizeof(epevout));
     memset(&epevin.data.ptr, 5, sizeof(epevin.data.ptr));
     epevin.events = EPOLLIN | EPOLLOUT;
+    epevin.data.fd = fildes[[1]];
 
-    if (epoll_ctl(epfd, EPOLL_CTL_ADD, fildes[[0]], &epevin) == -1)
+    if (epoll_ctl(epfd, EPOLL_CTL_ADD, fildes[[1]], &epevin) == -1)
         exit(1);
 
     res = epoll_wait(epfd, &epevout, 1, 0);
@@ -257,9 +258,10 @@ AC_INCLUDES_DEFAULT
     memset(&epevout, 0, sizeof(epevout));
     memset(&epevin.data.ptr, 5, sizeof(epevin.data.ptr));
     epevin.events = EPOLLIN | EPOLLOUT;
+    epevin.data.fd = fildes[[1]];
 
     if (syscall(__NR_epoll_ctl, epfd, 
-        EPOLL_CTL_ADD, fildes[[0]], &epevin) == -1)
+        EPOLL_CTL_ADD, fildes[[1]], &epevin) == -1)
         exit(1);
 
     res = syscall(__NR_epoll_wait, epfd, &epevout, 1, 0);