Import "glob" and "getcwd" modules from gnulib

Import "glob" and "getcwd" modules from gnulib

These two modules are necessary because of the rework that will be
done in the "change directory" logic on GDB/gdbserver in the next
commits.

First, we will get rid of the "gdb_dirbuf" global variable and instead
rely on the fact that "getcwd (NULL, 0)", which is a GNU extension,
returns a heap-allocated string with the necessary bytes to hold the
full path.  This is a good practice not only because globals are not
ideal but also because there is no good way to know beforehand the
size of the full pathname allowed in the filesystem ("PATH_MAX" is not
portable and does not reflect all the possible filesystems out there).

We will also have a way to "cd" to a directory also on gdbserver, but
in order to do that uniformly, there must be a way to do tilde
expansion on directories provided by the user.  Currently, GDB uses
"tilde_expand" from readline to do that, but gdbserver doesn't link
against readline and therefore cannot use this function.  The solution
is to use "glob" instead, which can perform tilde expansion as a GNU
extension.  Therefore, we need gnulib's version of "glob".

A special note is necessary for gdb/ser-tcp.c.  It defines "close" as
"closesocket" on Win32 targets.  If we leave the code as is, this
would conflict with gnulib's definition of "close".  Therefore, in
order to keep the same code path from before this import, I decided to
"#undef close" first, and then let the original (re)definition of it
take place.

gdb/ChangeLog:
2017-09-22  Sergio Durigan Junior  <sergiodj@redhat.com>

	* gnulib/aclocal.m4: Regenerate.
	* gnulib/config.in: Regenerate.
	* gnulib/configure: Regenerate.
	* gnulib/import/Makefile.am: Regenerate.
	* gnulib/import/Makefile.in: Regenerate.
	* gnulib/import/assure.h: New file.
	* gnulib/import/at-func.c: Likewise
	* gnulib/import/chdir-long.c: New file.
	* gnulib/import/chdir-long.h: New file.
	* gnulib/import/cloexec.c: New file.
	* gnulib/import/cloexec.h: New file.
	* gnulib/import/close.c: New file.
	* gnulib/import/closedir.c: New file.
	* gnulib/import/dirent-private.h: New file.
	* gnulib/import/dup-safer.c: New file.
	* gnulib/import/dup.c: New file.
	* gnulib/import/dup2.c: New file.
	* gnulib/import/error.c: New file.
	* gnulib/import/error.h: New file.
	* gnulib/import/exitfail.c: New file.
	* gnulib/import/exitfail.h: New file.
	* gnulib/import/fchdir.c: New file.
	* gnulib/import/fcntl.c: New file.
	* gnulib/import/fcntl.in.h: New file.
	* gnulib/import/fd-hook.c: New file.
	* gnulib/import/fd-hook.h: New file.
	* gnulib/import/fd-safer.c: New file.
	* gnulib/import/fdopendir.c: New file.
	* gnulib/import/filename.h: New file.
	* gnulib/import/filenamecat-lgpl.c: New file.
	* gnulib/import/filenamecat.h: New file.
	* gnulib/import/fstat.c: New file.
	* gnulib/import/fstatat.c: New file.
	* gnulib/import/getcwd-lgpl.c: New file.
	* gnulib/import/getcwd.c: New file.
	* gnulib/import/getdtablesize.c: New file.
	* gnulib/import/getlogin_r.c: New file.
	* gnulib/import/getprogname.c: New file.
	* gnulib/import/getprogname.h: New file.
	* gnulib/import/gettext.h: New file.
	* gnulib/import/glob-libc.h: New file.
	* gnulib/import/glob.c: New file.
	* gnulib/import/glob.in.h: New file.
	* gnulib/import/intprops.h: New file.
	* gnulib/import/m4/chdir-long.m4: New file.
	* gnulib/import/m4/close.m4: New file.
	* gnulib/import/m4/closedir.m4: New file.
	* gnulib/import/m4/d-ino.m4: New file.
	* gnulib/import/m4/d-type.m4: New file.
	* gnulib/import/m4/dup.m4: New file.
	* gnulib/import/m4/dup2.m4: New file.
	* gnulib/import/m4/error.m4: New file.
	* gnulib/import/m4/fchdir.m4: New file.
	* gnulib/import/m4/fcntl.m4: New file.
	* gnulib/import/m4/fcntl_h.m4: New file.
	* gnulib/import/m4/fdopendir.m4: New file.
	* gnulib/import/m4/filenamecat.m4: New file.
	* gnulib/import/m4/fstat.m4: New file.
	* gnulib/import/m4/fstatat.m4: New file.
	* gnulib/import/m4/getcwd-abort-bug.m4: New file.
	* gnulib/import/m4/getcwd-path-max.m4: New file.
	* gnulib/import/m4/getcwd.m4: New file.
	* gnulib/import/m4/getdtablesize.m4: New file.
	* gnulib/import/m4/getlogin_r.m4: New file.
	* gnulib/import/m4/getprogname.m4: New file.
	* gnulib/import/m4/glob.m4: New file.
	* gnulib/import/m4/gnulib-cache.m4: Regenerate.
	* gnulib/import/m4/gnulib-comp.m4: Regenerate.
	* gnulib/import/m4/mempcpy.m4: New file.
	* gnulib/import/m4/memrchr.m4: New file.
	* gnulib/import/m4/mode_t.m4: New file.
	* gnulib/import/m4/msvc-inval.m4: New file.
	* gnulib/import/m4/msvc-nothrow.m4: New file.
	* gnulib/import/m4/open.m4: New file.
	* gnulib/import/m4/openat.m4: New file.
	* gnulib/import/m4/opendir.m4: New file.
	* gnulib/import/m4/readdir.m4: New file.
	* gnulib/import/m4/realloc.m4: New file.
	* gnulib/import/m4/rewinddir.m4: New file.
	* gnulib/import/m4/save-cwd.m4: New file.
	* gnulib/import/m4/strdup.m4: New file.
	* gnulib/import/m4/strerror.m4: New file.
	* gnulib/import/m4/unistd-safer.m4: New file.
	* gnulib/import/mempcpy.c: New file.
	* gnulib/import/memrchr.c: New file.
	* gnulib/import/msvc-inval.c: New file.
	* gnulib/import/msvc-inval.h: New file.
	* gnulib/import/msvc-nothrow.c: New file.
	* gnulib/import/msvc-nothrow.h: New file.
	* gnulib/import/open.c: New file.
	* gnulib/import/openat-die.c: New file.
	* gnulib/import/openat-priv.h: New file.
	* gnulib/import/openat-proc.c: New file.
	* gnulib/import/openat.c: New file.
	* gnulib/import/openat.h: New file.
	* gnulib/import/opendir.c: New file.
	* gnulib/import/pipe-safer.c: New file.
	* gnulib/import/readdir.c: New file.
	* gnulib/import/realloc.c: New file.
	* gnulib/import/rewinddir.c: New file.
	* gnulib/import/save-cwd.c: New file.
	* gnulib/import/save-cwd.h: New file.
	* gnulib/import/strdup.c: New file.
	* gnulib/import/strerror-override.c: New file.
	* gnulib/import/strerror-override.h: New file.
	* gnulib/import/strerror.c: New file.
	* gnulib/import/unistd--.h: New file.
	* gnulib/import/unistd-safer.h: New file.
	* gnulib/update-gnulib.sh (IMPORTED_GNULIB_MODULES): Add
	"getcwd" and "glob".
	* ser-tcp.c: Undefine "close" before redefining it.