bash: Update the patches applied to bash

bash: Update the patches applied to bash

- Update the patches to include patches 16 to 21
- Update of rootfile not required
- Changelog
	patch 21: fix for expanding command substitutions in a word expansion in a
		  here-document
	patch 20: allow time reserved word as first token in command substitution
	patch 19: fix case where background job set the terminal process group
	patch 18: fix for returning unknown tokens to the bison parser
	patch 17: fix for optimizing forks when using the . builtin in a subshell
	patch 16: fix for a crash if one of the expressions in an arithmetic for command
		  expands to NULL

Signed-off-by: Adolf Belka <adolf.belka@ipfire.org>
Reviewed-by: Peter Müller <peter.mueller@ipfire.org>