Add support for V4L2.

Index: plugins/CMakeLists.txt
--- plugins/CMakeLists.txt.orig
+++ plugins/CMakeLists.txt
@@ -57,6 +57,7 @@ elseif("${CMAKE_SYSTEM_NAME}" MATCHES "FreeBSD")
 	add_subdirectory(sndio)
 elseif("${CMAKE_SYSTEM_NAME}" MATCHES "OpenBSD")
 	add_subdirectory(linux-capture)
+	add_subdirectory(linux-v4l2)
 	add_subdirectory(sndio)
 endif()
 
