videorec: Fix flushing encoders
When passing NULL frames, encoders empty their queues, but we have
to stop polling from them when they don't any more data.
if(WIN32 AND NOT UNIX) file(GLOB DLLs *.dll) file(GLOB ICOs *.ico) install(FILES ${DLLs} ${ICOs} DESTINATION ${target_library_install_dir})endif(WIN32 AND NOT UNIX)