Remove stime backport.

Remove static libgcc patch as upstream fixed it with
BUSYBOX_DEFAULT_STATIC_LIBGCC which defauls to off.

Remove date -k patch as it no longer applies. It's also pointless as
busybox' hwclock utility can do the same thing.

Remove ntpd patch as that seems to have been applied upstream.

Add smalll patch fixing compilation with SELinux. Upstream commit
2496616b0a8d1c80cd1416b73a4847b59b9f969a renamed the variable without
renaming it in the SELinux path.

Refresh config and patches.

Config refresh:

Refresh commands, run after busybox is first built once:

  cd package/utils/busybox/config/
  ../convert_menuconfig.pl ../../../../build_dir/target-mips_24kc_musl/busybox-default/busybox-1.33.0
  cd ..
  ./convert_defaults.pl < ../../../build_dir/target-mips_24kc_musl/busybox-default/busybox-1.33.0/.config > Config-defaults.in

Manual edits needed afterward:

* Config-defaults.in:  OpenWrt config symbol IPV6 logic applied to
  BUSYBOX_DEFAULT_FEATURE_IPV6
* Config-defaults.in:  OpenWrt configTARGET_bcm53xx logic applied to
  BUSYBOX_DEFAULT_TRUNCATE (commit 547f1ec2)
* editors/Config.in: Add USE_GLIBC dependency to
  BUSYBOX_CONFIG_FEATURE_VI_REGEX_SEARCH (commit f1410902)
* shell/Config.in : change at "Options common to all shells"  the symbol
  SHELL_ASH  -->  BUSYBOX_CONFIG_SHELL_ASH
   (discussion in http://lists.openwrt.org/pipermail/openwrt-devel/2021-January/033140.html


     Apparently our script does not see the hidden option while
     prepending config options with "BUSYBOX_CONFIG_" which leads to a
     missed dependency when the options are later evaluated.)
* Edit Config.in files by adding quotes to sourced items in
  config/Config.in, networking/Config.in and util-linux/Config.in (commit 1da014fc)

Signed-off-by: Hauke Mehrtens <hauke@hauke-m.de>
[Added comments from Hannu Nyman to commit message]
Signed-off-by: Rosen Penev <rosenp@gmail.com>