Provide group read, write and execute permissions for /dev/dvb, otherwise
adapters will not be accessible from tvheadend.

Signed-off-by: Matthew Hagan <mnhagan88@gmail.com>

Changes:
- Update to tvheadend git master branch,
  commit 2efe90cdcf
  dated 2021-11-16
- Removed patches that are not needed anymore.
- Add patch to ignore a ICONV test that runs at tvheadned startup.
  This test fails without "full language support" in OpenWrt,
  but tvheadend appears to run fine anyway.
- Descrambling needs libdvbcsa, a BUILD_PATENTED package.
  Control Word clients now depend on descrambling.
- Added options:
  - CCCAM client
  - RegEx library choice: POSIX (internal) / libpcre (more compatible) / libpcre2
  - Optimize for speed (-O3, LTO)
- FFMPEG is working again. Added options for transcoding, but commented-out.
  If anyone needs this, just uncomment, make menuconfig and build.
- Sort everything in a more logical order

Signed-off-by: Marius Dinu <m95d+git@psihoexpert.ro>

- Added menuconfig options:
  - TV sources and protocols: SAT>IP, IPTV, HDHomeRun
  - SoftCAM (3 options)
  - Image cache (default changed to OFF)
  - Trace debug option (default changed to OFF)
- Added menuconfig descriptions.
- Removed codecs.
- Made PIE option dependent on global OpenWRT PIE setting.
- Run as regular user, not root.
- Added USB hotplug script to change DVB tuners permissions.
- Fixed a first-start bug(?) that I encountered: admin account created but not saved.

Signed-off-by: Marius Dinu <m95d+git@psihoexpert.ro>