dropbear: bump to 2018.76

dropbear: bump to 2018.76

- drop patches applied upstream:
  * 010-runtime-maxauthtries.patch
  * 150-dbconvert_standalone.patch
  * 610-skip-default-keys-in-custom-runs.patch
- drop patches backported to previous version,
  because they need to be reapplied to current version:
  * 020-Wait-to-fail-invalid-usernames.patch
- refresh patches
- move OpenWrt configuration from patch to Build/Configure recipe,
  thus drop patch 120-openwrt_options.patch
- update copyright years

Signed-off-by: Konstantin Demin <[email protected]>