gnulib: Update gnulib version and drop most gnulib patches

In addition to the changes carried in our gnulib patches, several
Coverity and code hygiene fixes that were previously downstream are also
included in this 3-year gnulib increment.

Unfortunately, fix-width.patch is retained.

Bump minimum autoconf version from 2.63 to 2.64 and automake from 1.11
to 1.14, as required by gnulib.

Sync bootstrap script itself with gnulib.

Update regexp module for new dynarray dependency.

Signed-off-by: Robbie Harwood <rharwood@redhat.com>
Reviewed-by: Daniel Kiper <daniel.kiper@oracle.com>

grub-core/lib/gnulib-patches/fix-unused-value.patch

@@ -1,14 +0,0 @@
---- a/lib/regexec.c	2020-10-21 14:25:35.310195912 +0000
-+++ b/lib/regexec.c	2020-10-21 14:32:07.961765604 +0000
-@@ -828,7 +828,11 @@
- 		    break;
- 		  if (__glibc_unlikely (err != REG_NOMATCH))
- 		    goto free_return;
-+#ifdef DEBUG
-+		  /* Only used for assertion below when DEBUG is set, otherwise
-+		     it will be over-written when we loop around.  */
- 		  match_last = -1;
-+#endif
- 		}
- 	      else
- 		break; /* We found a match.  */