gr_pwin32.m4: Replace inline sleep() function

Building libltdl recursively with MinGW failed with an error of "sleep"
being redefined.  Commenting out the sleep() definition in config.h.in
resulted in libtdl compiling but a linker failure in libyaesu as
"_sleep" was not defined.

A bit of searching reveals that the MS Windows API does not include
"sleep" and MinGW does not include it either, hence the definition in
gr_pwin32.m4 from the GNU Radio project.  Uopn finding a MinGW User
thread from 2007 that discussed this very issue, the following message
hinted that using a CPP #define to wrap Windows Sleep() may work:

http://mingw.5.n7.nabble.com/Help-where-is-the-C-language-sleep-function-tp8921p8925.html

And indeed it seems to.  Compilation is now clean with recursive libltdl
and the rest of Hamlib, but does it work?

macros/gr_pwin32.m4

@@ -1,19 +1,19 @@
 # Check for (mingw)win32 POSIX replacements.             -*- Autoconf -*-
 
 # Copyright 2003 Free Software Foundation, Inc.
-# 
+#
 # This file is part of GNU Radio
-# 
+#
 # GNU Radio is free software; you can redistribute it and/or modify
 # it under the terms of the GNU General Public License as published by
 # the Free Software Foundation; either version 2, or (at your option)
 # any later version.
-# 
+#
 # GNU Radio is distributed in the hope that it will be useful,
 # but WITHOUT ANY WARRANTY; without even the implied warranty of
 # MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 # GNU General Public License for more details.
-# 
+#
 # You should have received a copy of the GNU General Public License
 # along with GNU Radio; see the file COPYING.  If not, write to
 # the Free Software Foundation, Inc., 59 Temple Place - Suite 330,
@@ -89,7 +89,8 @@ int usleep(unsigned long usec);	/* SUSv2 */
 #include <winbase.h>
 #endif
 /* TODO: what about SleepEx? */
-static inline unsigned int sleep (unsigned int nb_sec) { Sleep(nb_sec*1000); return 0; }
+/* static inline unsigned int sleep (unsigned int nb_sec) { Sleep(nb_sec*1000); return 0; } */
+#define sleep(seconds) Sleep((seconds)*1000)
 #endif
 
 #ifndef HAVE_GETTIMEOFDAY