package/libplatform: new package

Needed by libcec 3.x

[Thomas:
  - adjust licensing information: license is not GPLv3+, but GPLv2+
    plus one source file in PHP license v3.01.
  - add proper license files.
  - remove the -DCMAKE_MODULE_PATH=$(STAGING_DIR)/usr/lib/kodi since
    it doesn't seem to be necessary
  - add patch to fix invalid header and library paths in
    platform-config.cmake.]

Signed-off-by: Bernd Kuhls <bernd.kuhls@t-online.de>
Signed-off-by: Thomas Petazzoni <thomas.petazzoni@free-electrons.com>