Move gnulib to top level

This patch moves the gdb/gnulib subdirectory to the top level.

It adjusts the top-level build system to build gnulib when necessary,
and changes gdb to use this.  However, gdbserver still builds its own
copy of gnulib, just from the new source location.

A small hack was needed to ensure that gnulib is only built when gdb
is enabled.  The Makefile only provides an ordering -- the directory
must be mentioned in configdirs to actually be compiled at all.

Most of the patch is just a "git mv" of gnulib, though a few minor
path adjustments were needed in some files there.

Tested by the buildbot.

ChangeLog
2019-06-14  Tom Tromey  <tom@tromey.com>

	* MAINTAINERS: Add gnulib.
	* gnulib: New directory, move from gdb/gnulib.
	* configure.ac (host_libs): Add gnulib.
	* configure: Rebuild.
	* Makefile.def (host_modules, dependencies): Add gnulib.
	* Makefile.in: Rebuild.

gdb/ChangeLog
2019-06-14  Tom Tromey  <tom@tromey.com>

	* gnulib: Move directory to top-level.
	* configure.ac: Don't configure gnulib.
	* configure: Rebuild.
	* common/common-defs.h: Use new path to gnulib.
	* Makefile.in (GNULIB_BUILDDIR): Now ../gnulib.
	(GNULIB_H): Remove.
	(INCGNU): Look in new gnulib location.
	(HFILES_NO_SRCDIR): Remove gnulib files.
	(SUBDIR, REQUIRED_SUBDIRS): Remove gnulib.
	(generated_files): Remove GNULIB_H.
	($(LIBGNU), all-lib): Remove targets.
	(distclean): Don't mention GNULIB_BUILDDIR.
	($(GNULIB_BUILDDIR)/Makefile): Remove target.

gdb/gdbserver/ChangeLog
2019-06-14  Tom Tromey  <tom@tromey.com>

	* configure.ac: Use new path to gnulib.
	* configure: Rebuild.
	* Makefile.in (INCGNU, $(GNULIB_BUILDDIR)/Makefile): Use new path
	to gnulib.

gnulib/ChangeLog
2019-06-14  Tom Tromey  <tom@tromey.com>

	* update-gnulib.sh: Adjust paths.
	* Makefile.in: Adjust paths.
	* configure.ac: Adjust paths.  Use ACX_LARGEFILE.
	* configure: Rebuild.

gnulib/import/getdtablesize.c

@@ -0,0 +1,121 @@
+/* getdtablesize() function for platforms that don't have it.
+   Copyright (C) 2008-2016 Free Software Foundation, Inc.
+   Written by Bruno Haible <bruno@clisp.org>, 2008.
+
+   This program 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 3 of the License, or
+   (at your option) any later version.
+
+   This program 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 this program.  If not, see <http://www.gnu.org/licenses/>.  */
+
+#include <config.h>
+
+/* Specification.  */
+#include <unistd.h>
+
+#if (defined _WIN32 || defined __WIN32__) && ! defined __CYGWIN__
+
+# include <stdio.h>
+
+# include "msvc-inval.h"
+
+# if HAVE_MSVC_INVALID_PARAMETER_HANDLER
+static int
+_setmaxstdio_nothrow (int newmax)
+{
+  int result;
+
+  TRY_MSVC_INVAL
+    {
+      result = _setmaxstdio (newmax);
+    }
+  CATCH_MSVC_INVAL
+    {
+      result = -1;
+    }
+  DONE_MSVC_INVAL;
+
+  return result;
+}
+#  define _setmaxstdio _setmaxstdio_nothrow
+# endif
+
+/* Cache for the previous getdtablesize () result.  Safe to cache because
+   Windows also lacks setrlimit.  */
+static int dtablesize;
+
+int
+getdtablesize (void)
+{
+  if (dtablesize == 0)
+    {
+      /* We are looking for the number N such that the valid file descriptors
+         are 0..N-1.  It can be obtained through a loop as follows:
+           {
+             int fd;
+             for (fd = 3; fd < 65536; fd++)
+               if (dup2 (0, fd) == -1)
+                 break;
+             return fd;
+           }
+         On Windows XP, the result is 2048.
+         The drawback of this loop is that it allocates memory for a libc
+         internal array that is never freed.
+
+         The number N can also be obtained as the upper bound for
+         _getmaxstdio ().  _getmaxstdio () returns the maximum number of open
+         FILE objects.  The sanity check in _setmaxstdio reveals the maximum
+         number of file descriptors.  This too allocates memory, but it is
+         freed when we call _setmaxstdio with the original value.  */
+      int orig_max_stdio = _getmaxstdio ();
+      unsigned int bound;
+      for (bound = 0x10000; _setmaxstdio (bound) < 0; bound = bound / 2)
+        ;
+      _setmaxstdio (orig_max_stdio);
+      dtablesize = bound;
+    }
+  return dtablesize;
+}
+
+#else
+
+# include <limits.h>
+# include <sys/resource.h>
+
+# ifndef RLIM_SAVED_CUR
+#  define RLIM_SAVED_CUR RLIM_INFINITY
+# endif
+# ifndef RLIM_SAVED_MAX
+#  define RLIM_SAVED_MAX RLIM_INFINITY
+# endif
+
+# ifdef __CYGWIN__
+  /* Cygwin 1.7.25 auto-increases the RLIMIT_NOFILE soft limit until it
+     hits the compile-time constant hard limit of 3200.  We might as
+     well just report the hard limit.  */
+#  define rlim_cur rlim_max
+# endif
+
+int
+getdtablesize (void)
+{
+  struct rlimit lim;
+
+  if (getrlimit (RLIMIT_NOFILE, &lim) == 0
+      && 0 <= lim.rlim_cur && lim.rlim_cur <= INT_MAX
+      && lim.rlim_cur != RLIM_INFINITY
+      && lim.rlim_cur != RLIM_SAVED_CUR
+      && lim.rlim_cur != RLIM_SAVED_MAX)
+    return lim.rlim_cur;
+
+  return INT_MAX;
+}
+
+#endif