check for a fine poll() before it is used to sleep subsecond

configure.ac

@@ -1201,6 +1201,31 @@ if test "$ac_cv_func_sigsetjmp" != "yes"; then
                )
 fi
 
+dnl poll() might be badly emulated, as in Mac OS X 10.3 (and other BSDs?) and
+dnl to find out we make an extra check here!
+if test "$ac_cv_func_poll" = "yes"; then
+  AC_MSG_CHECKING([if poll works with NULL inputs])
+  AC_RUN_IFELSE([
+#ifdef HAVE_SYS_POLL_H
+#include <sys/poll.h>
+#endif
+
+  int main(void)
+  {
+    /* make this return 0 == timeout since there's nothing to read from */
+    return poll((void *)0, 0, 10 /*ms*/);
+  }
+],
+  AC_MSG_RESULT(yes)
+  AC_DEFINE(HAVE_POLL_FINE, 1, [If you have a fine poll]),
+  AC_MSG_RESULT(no),
+  AC_MSG_RESULT(cross-compiling assumes yes)
+  AC_DEFINE(HAVE_POLL_FINE, 1, [If you have a fine poll])
+  ) dnl end of AC_RUN_IFELSE
+fi
+
+
+
 AC_PATH_PROG( PERL, perl, , 
   $PATH:/usr/local/bin/perl:/usr/bin/:/usr/local/bin )
 AC_SUBST(PERL)