- Add header tests for `error.h`, `sys/types.h` and `sys/select.h`
- Add function tests for `canonicalize_file_name()` and `fopencookie()`
- Add `compat.h` header to provide replacements for `error()`,
`error_at_line()` and `canonicalize_file_name()` as well as the
`_PATH_MOUNTED` and `_PATH_MNTTAB` defines
- Add missing includes for `sys/select.h` and `sys/types.h`
- Disable libneon debugging if no `fopencookie()` implementation is
available
Signed-off-by: Jo-Philipp Wich <jow@openwrt.org>
