Fix build with glibc 2.28

glibc 2.28 hides a number of internal macros that used to be visible. gnulib
relied on these macros. Add a patch based on upstream gnulib commit
4af4a4a71827c0 (fflush: adjust to glibc 2.28 libio.h removal) to fix the
build.

Signed-off-by: Baruch Siach <baruch@tkos.co.il>
---
Upstream status: gnulib commit 4af4a4a7182

diff -Nuar dc3dd-7.2.641.orig/lib/freadahead.c dc3dd-7.2.641/lib/freadahead.c
--- dc3dd-7.2.641.orig/lib/freadahead.c	2012-11-06 23:42:58.000000000 +0200
+++ dc3dd-7.2.641/lib/freadahead.c	2018-10-26 08:46:36.612492230 +0300
@@ -24,7 +24,7 @@
 size_t
 freadahead (FILE *fp)
 {
-#if defined _IO_ferror_unlocked || __GNU_LIBRARY__ == 1 /* GNU libc, BeOS, Linux libc5 */
+#if defined _IO_EOF_SEEN || defined _IO_ferror_unlocked || __GNU_LIBRARY__ == 1 /* GNU libc, BeOS, Linux libc5 */
   if (fp->_IO_write_ptr > fp->_IO_write_base)
     return 0;
   return (fp->_IO_read_end - fp->_IO_read_ptr)
diff -Nuar dc3dd-7.2.641.orig/lib/freadptr.c dc3dd-7.2.641/lib/freadptr.c
--- dc3dd-7.2.641.orig/lib/freadptr.c	2012-11-06 23:42:58.000000000 +0200
+++ dc3dd-7.2.641/lib/freadptr.c	2018-10-26 08:36:53.965310494 +0300
@@ -29,7 +29,7 @@
   size_t size;
 
   /* Keep this code in sync with freadahead!  */
-#if defined _IO_ferror_unlocked || __GNU_LIBRARY__ == 1 /* GNU libc, BeOS, Linux libc5 */
+#if defined _IO_EOF_SEEN || defined _IO_ferror_unlocked || __GNU_LIBRARY__ == 1 /* GNU libc, BeOS, Linux libc5 */
   if (fp->_IO_write_ptr > fp->_IO_write_base)
     return NULL;
   size = fp->_IO_read_end - fp->_IO_read_ptr;
diff -Nuar dc3dd-7.2.641.orig/lib/freadseek.c dc3dd-7.2.641/lib/freadseek.c
--- dc3dd-7.2.641.orig/lib/freadseek.c	2012-11-06 23:42:58.000000000 +0200
+++ dc3dd-7.2.641/lib/freadseek.c	2018-10-26 08:49:35.387912087 +0300
@@ -34,7 +34,7 @@
 freadptrinc (FILE *fp, size_t increment)
 {
   /* Keep this code in sync with freadptr!  */
-#if defined _IO_ferror_unlocked || __GNU_LIBRARY__ == 1 /* GNU libc, BeOS, Linux libc5 */
+#if defined _IO_EOF_SEEN || defined _IO_ferror_unlocked || __GNU_LIBRARY__ == 1 /* GNU libc, BeOS, Linux libc5 */
   fp->_IO_read_ptr += increment;
 #elif defined __sferror || defined __DragonFly__ /* FreeBSD, NetBSD, OpenBSD, DragonFly, MacOS X, Cygwin */
   fp_->_p += increment;
diff -Nuar dc3dd-7.2.641.orig/lib/fseeko.c dc3dd-7.2.641/lib/fseeko.c
--- dc3dd-7.2.641.orig/lib/fseeko.c	2012-11-06 23:42:58.000000000 +0200
+++ dc3dd-7.2.641/lib/fseeko.c	2018-10-26 08:51:02.841583936 +0300
@@ -44,7 +44,7 @@
 #endif
 
   /* These tests are based on fpurge.c.  */
-#if defined _IO_ferror_unlocked || __GNU_LIBRARY__ == 1 /* GNU libc, BeOS, Linux libc5 */
+#if defined _IO_EOF_SEEN || defined _IO_ferror_unlocked || __GNU_LIBRARY__ == 1 /* GNU libc, BeOS, Linux libc5 */
   if (fp->_IO_read_end == fp->_IO_read_ptr
       && fp->_IO_write_ptr == fp->_IO_write_base
       && fp->_IO_save_base == NULL)
diff -Nuar dc3dd-7.2.641.orig/lib/fseterr.c dc3dd-7.2.641/lib/fseterr.c
--- dc3dd-7.2.641.orig/lib/fseterr.c	2012-11-06 23:42:58.000000000 +0200
+++ dc3dd-7.2.641/lib/fseterr.c	2018-10-26 08:47:51.209919605 +0300
@@ -29,7 +29,7 @@
   /* Most systems provide FILE as a struct and the necessary bitmask in
      <stdio.h>, because they need it for implementing getc() and putc() as
      fast macros.  */
-#if defined _IO_ferror_unlocked || __GNU_LIBRARY__ == 1 /* GNU libc, BeOS, Linux libc5 */
+#if defined _IO_EOF_SEEN || defined _IO_ferror_unlocked || __GNU_LIBRARY__ == 1 /* GNU libc, BeOS, Linux libc5 */
   fp->_flags |= _IO_ERR_SEEN;
 #elif defined __sferror || defined __DragonFly__ /* FreeBSD, NetBSD, OpenBSD, DragonFly, MacOS X, Cygwin */
   fp_->_flags |= __SERR;
diff -Nuar dc3dd-7.2.641.orig/lib/stdio-impl.h dc3dd-7.2.641/lib/stdio-impl.h
--- dc3dd-7.2.641.orig/lib/stdio-impl.h	2012-11-06 23:42:58.000000000 +0200
+++ dc3dd-7.2.641/lib/stdio-impl.h	2018-10-26 08:46:26.136291709 +0300
@@ -18,6 +18,12 @@
    the same implementation of stdio extension API, except that some fields
    have different naming conventions, or their access requires some casts.  */
 
+/* Glibc 2.28 made _IO_IN_BACKUP private.  For now, work around this
+   problem by defining it ourselves.  FIXME: Do not rely on glibc
+   internals.  */
+#if !defined _IO_IN_BACKUP && defined _IO_EOF_SEEN
+# define _IO_IN_BACKUP 0x100
+#endif
 
 /* BSD stdio derived implementations.  */