cap_libv4l.cpp depends on both libv4l 1 and 2, so search for both

How this worked before, I do not know.

CMakeLists.txt

@@ -983,7 +983,8 @@ if(DEFINED WITH_V4L)
   else()
     set(HAVE_CAMV4L2_STR "NO")
   endif()
-  status("    V4L/V4L2:"       HAVE_LIBV4L         THEN "Using libv4l (ver ${ALIASOF_libv4l1_VERSION})"
+  status("    V4L/V4L2:"       HAVE_LIBV4L
+             THEN "Using libv4l1 (ver ${ALIASOF_libv4l1_VERSION}) / libv4l2 (ver ${ALIASOF_libv4l2_VERSION})"
              ELSE "${HAVE_CAMV4L_STR}/${HAVE_CAMV4L2_STR}")
 endif(DEFINED WITH_V4L)
 

cmake/OpenCVFindLibsVideo.cmake

@@ -153,7 +153,13 @@ endif(WITH_XINE)
 ocv_clear_vars(HAVE_LIBV4L HAVE_CAMV4L HAVE_CAMV4L2 HAVE_VIDEOIO)
 if(WITH_V4L)
   if(WITH_LIBV4L)
-    CHECK_MODULE(libv4l1 HAVE_LIBV4L)
+    CHECK_MODULE(libv4l1 HAVE_LIBV4L1)
+    CHECK_MODULE(libv4l2 HAVE_LIBV4L2)
+    if(HAVE_LIBV4L1 AND HAVE_LIBV4L2)
+      set(HAVE_LIBV4L YES)
+    else()
+      set(HAVE_LIBV4L NO)
+    endif()
   endif()
   CHECK_INCLUDE_FILE(linux/videodev.h HAVE_CAMV4L)
   CHECK_INCLUDE_FILE(linux/videodev2.h HAVE_CAMV4L2)