newt: Update to 0.52.21

newt: Update to 0.52.21

- Update newt from 0.52.18 to 0.52.21
- Updated rootfile
- Changelog
	0.52.21
	- define env NEWT_NOFLOWCTRL to disable flow control (Robert Gill)
	- don't leak memory on errors in dialogboxes
	- fix radio button selection check in snack
	- fix plural forms in Lithuanian translation (#1568999)
	- fix parallel build (Émeric Dupont)
	- allow python versions to be specified with --with-python option
	0.52.20
	- improve handling of long strings in whiptail menu (#1353792)
	- support screen resize as hotkey in form (#1432926)
	0.52.19
	- support --notags in whiptail checklist and radiolist (#1319794)
	- don't hard-code -I/usr/include/slang in CPPFLAGS (Alex Suykov)
	- use $(CC) instead of $(CPP) to generate .depend files (Samuel Martin)
	- update translations from Zanata

Signed-off-by: Adolf Belka <adolf.belka@ipfire.org>
Signed-off-by: Michael Tremer <michael.tremer@ipfire.org>