build-sys: determine availability of __fpending()

Needed to for making Cygwin more possible.

Reference: http://comments.gmane.org/gmane.linux.utilities.util-linux-ng/5656
Reported-by: Bernhard Voelker <bernhard.voelker@siemens-enterprise.com>
Signed-off-by: Sami Kerola <kerolasa@iki.fi>

configure.ac

@@ -152,6 +152,7 @@ AC_CHECK_HEADERS([ \
 	pty.h \
 	security/pam_misc.h \
 	stdint.h \
+	stdio_ext.h \
 	stdlib.h \
 	sys/disk.h \
 	sys/disklabel.h \
@@ -245,6 +246,7 @@ AC_CHECK_DECL([lseek64],
 	 #include <unistd.h>])
 
 AC_CHECK_FUNCS([ \
+	__fpending \
 	__secure_getenv \
 	err \
 	errx \

include/closestream.h

@@ -2,12 +2,22 @@
 #define UTIL_LINUX_CLOSESTREAM_H
 
 #include <stdio.h>
+#ifdef HAVE_STDIO_EXT_H
 #include <stdio_ext.h>
+#endif
 #include <unistd.h>
 
 #include "c.h"
 #include "nls.h"
 
+#ifndef HAVE___FPENDING
+static inline int
+__fpending(FILE *stream __attribute__((__unused__)))
+{
+	return 0;
+}
+#endif
+
 static inline int
 close_stream(FILE * stream)
 {