package/gerbera: security bump to version 1.6.4

package/gerbera: security bump to version 1.6.4

- This version is compatible with libupnp 1.14.x which fix
  CallStranger a.k.a. CVE-2020-12695
- Drop all patches (already in version)
- expat is not needed since version 1.5.0 and
  https://github.com/gerbera/gerbera/commit/a4f0cccd6a1f741c55ca69b06cff3a964eebc1f3
- fmt is a mandatory dependency since version 1.5.0 and
  https://github.com/gerbera/gerbera/commit/fe81e5fc8898d6e3a53ce30ddaafb8439683f46f
- spdlog is a mandatory dependency since version 1.5.0 and
  https://github.com/gerbera/gerbera/commit/615d698fe4dce9d7462022a00c74af1fac7a1003
- pugixml is a mandatory dependency since version 1.5.0 and
  https://github.com/gerbera/gerbera/commit/c244006aa04ab2e4c5f3e7003ca727e05440238d
- libnpupnp can be used instead of libupnp since version 1.6.2 and
  https://github.com/gerbera/gerbera/commit/e648763626e3c2512801bd127a0a3b96c8716faf
- Set CXX_FILESYSTEM_NO_LINK_NEEDED to ON to avoid a build failure
  due to check_cxx_source_runs which has been added with
  https://github.com/gerbera/gerbera/commit/8ea0fce24ce9b1cf870837c3be984fed50581dfb
- Update indentation in hash file (two spaces)

Signed-off-by: Fabrice Fontaine <fontaine.fabrice@gmail.com>
[yann.morin.1998@free.fr:
  - libupnp and libnpupnp are mutually exclusive
  - fix typo in npupnp package name
]
Signed-off-by: Yann E. MORIN <yann.morin.1998@free.fr>