poll: fix compilation on BeOS

[Bruno Haible]

This fixes a compilation error on BeOS. The BeOS doc says that the flags
passed to socket functions should always be 0; there is no MSG_PEEK.


2007-03-22  Bruno Haible  <address@hidden>

        * lib/poll.c (MSG_PEEK): New fallback definition.

*** lib/poll.c  22 Jan 2007 09:33:16 -0000      1.8
--- lib/poll.c  23 Mar 2007 02:09:33 -0000
***************
*** 47,52 ****
--- 47,57 ----
  #define EOVERFLOW EINVAL
  #endif
  
+ /* BeOS does not have MSG_PEEK.  */
+ #ifndef MSG_PEEK
+ #define MSG_PEEK 0
+ #endif
+ 
  int
  poll (pfd, nfd, timeout)
       struct pollfd *pfd;