bootstrap: Fix patching warnings

Currently bootstrap complains in the following way when
patching gnulib files:

  patching file regcomp.c
  Hunk #2 succeeded at 1029 with fuzz 2.
  Hunk #5 succeeded at 1716 with fuzz 2.
  patching file regexec.c
  patching file base64.c
  patching file regexec.c
  Hunk #1 succeeded at 807 (offset -21 lines).

Let's fix it by adding missing "\f" and amending line
numbers in the patches.

Signed-off-by: Daniel Kiper <daniel.kiper@oracle.com>
Reviewed-by: Alec Brown <alec.r.brown@oracle.com>

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

@@ -1,6 +1,6 @@
 --- 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 @@
+@@ -807,7 +807,11 @@
  		    break;
  		  if (__glibc_unlikely (err != REG_NOMATCH))
  		    goto free_return;