Check for sendfile().

git-svn-id: http://www.varnish-cache.org/svn/trunk/varnish-cache@957 d4fa192b-c00b-0410-8231-f00ffab90ce4

configure.ac

@@ -64,6 +64,7 @@ AC_CHECK_FUNCS([strerror])
 AC_FUNC_STRERROR_R
 AC_CHECK_FUNCS([socket])
 AC_CHECK_FUNCS([strptime])
+AC_CHECK_FUNCS([sendfile])
 
 # These functions are provided by libcompat on platforms where they
 # are not available