Fix build with old kernel headers

* strace.c (print_debug_info, maybe_allocate_tcb, print_signalled,
print_exited): Remove "const" qualifier from status variable to
workaround some old implementations of WIFSIGNALED/WIFSTOPPED/WIFEXITED
macros.
* v4l2.c: Include <linux/types.h>.
(v4l2_ioctl): Check that V4L2_CTRL_FLAG_NEXT_CTRL and VIDIOC_S_EXT_CTRLS
macros are defined.
* tests/Makefile.am (AM_CPPFLAGS): Define.
3 files changed