Don't check for FIONREAD on windows.

Execution of platforms tests are slow/flaky when building on windows.
in PB:mysql-next-mr-opt-team on 2011-05-18 for win x86 debug_max, i see:
-- Looking for FIONREAD
-- Looking for FIONREAD - found
and the build fails.

cmake/os/WindowsCache.cmake

@@ -341,6 +341,7 @@ SET(SIGNAL_RETURN_TYPE_IS_VOID 1 CACHE INTERNAL "")
 SET(C_HAS_inline CACHE INTERNAL "")
 SET(C_HAS___inline 1 CACHE INTERNAL "")
 SET(FIONREAD_IN_SYS_IOCTL CACHE INTERNAL "")
+SET(FIONREAD_IN_SYS_FILIO CACHE INTERNAL "")
 SET(GWINSZ_IN_SYS_IOCTL CACHE INTERNAL "")
 SET(HAVE_CXXABI_H CACHE INTERNAL "")
 SET(HAVE_NDIR_H CACHE INTERNAL "")