add and consolidate nasty stdio_ext junk

hopefully this resolves the rest of the issues with hideously
nonportable hacks in programs that use gnulib.

include/stdio_ext.h

+#ifndef _STDIO_EXT_H
+#define _STDIO_EXT_H
+
+#ifdef __cplusplus
+extern "C" {
+#endif
+
+#define FSETLOCKING_QUERY 0
+#define FSETLOCKING_INTERNAL 1
+#define FSETLOCKING_BYCALLER 2
+
+void _flushlbf(void);
+int __fsetlocking(FILE *, int);
+int __fwriting(FILE *);
+int __freading(FILE *);
+int __freadable(FILE *);
+int __fwritable(FILE *);
+int __flbf(FILE *);
+size_t __fbufsize(FILE *);
+size_t __fpending(FILE *);
+int __fpurge(FILE *);
+
+#ifdef __cplusplus
+}
+#endif
+
+#endif

src/stdio/__fpending.c

-#include "stdio_impl.h"
-
-size_t __fpending(FILE *f)
-{
-	return f->wend ? f->wpos - f->wbase : 0;
-}

src/stdio/ext.c

+#define _GNU_SOURCE
+#include "stdio_impl.h"
+#include <stdio_ext.h>
+
+void _flushlbf(void)
+{
+	fflush(0);
+}
+
+int __fsetlocking(FILE *f, int type)
+{
+	return 0;
+}
+
+int __fwriting(FILE *f)
+{
+	return f->wend > f->wpos;
+}
+
+int __freading(FILE *f)
+{
+	return f->rend > f->rpos;
+}
+
+int __freadable(FILE *f)
+{
+	return !(f->flags & F_NORD);
+}
+
+int __fwritable(FILE *f)
+{
+	return !(f->flags & F_NOWR);
+}
+
+int __flbf(FILE *f)
+{
+	return f->lbf >= 0;
+}
+
+size_t __fbufsize(FILE *f)
+{
+	return f->buf_size;
+}
+
+size_t __fpending(FILE *f)
+{
+	return f->wend ? f->wpos - f->wbase : 0;
+}
+
+int __fpurge(FILE *f)
+{
+	f->wpos = f->wbase = f->wend = 0;
+	f->rpos = f->rend = 0;
+	return 0;
+}
+
+weak_alias(__fpurge, fpurge);

src/stdio/fpurge.c

-#define _GNU_SOURCE
-#include "stdio_impl.h"
-
-int __fpurge(FILE *f)
-{
-	f->wpos = f->wbase = f->wend = 0;
-	f->rpos = f->rend = 0;
-	return 0;
-}
-
-weak_alias(__fpurge, fpurge);