gnulib: sync from latest gnulib, notably bootstrap and parse-datetime

* bootstrap: Sync from gnulib.
* doc/.gitignore: Rename getdate.texi to parse-datetime.texi.
* doc/Makefile.am (tar_TEXINFOS): Likewise.
* doc/tar.texi (Top): Adjust to renaming of getdate to parse-datetime.
* gnulib.modules: Likewise.  Also, remove ftruncate (now obsolete).
And add inttostr (we missed this dependency).
* src/tar.c: Include parse-datetime.h, not getdate.h.  All calls
to get_date replaced with parse_datetime.

src/tar.c

@@ -43,7 +43,7 @@
 #include <closeout.h>
 #include <configmake.h>
 #include <exitfail.h>
-#include <getdate.h>
+#include <parse-datetime.h>
 #include <rmt.h>
 #include <rmt-command.h>
 #include <prepargs.h>
@@ -1023,7 +1023,7 @@ get_date_or_file (struct tar_args *args, const char *option,
     }
   else
     {
-      if (! get_date (ts, str, NULL))
+      if (! parse_datetime (ts, str, NULL))
 	{
 	  WARN ((0, 0, _("Substituting %s for unknown date format %s"),
 		 tartime (*ts, false), quote (str)));