Handle CONFIG_USER_NS/CONFIG_UIDGID_STRICT_TYPE_CHECKS in the runtime.

Handle CONFIG_USER_NS/CONFIG_UIDGID_STRICT_TYPE_CHECKS in the runtime.

* runtime/linux/task_finder.c: Add CONFIG_UIDGID_STRICT_TYPE_CHECKS code.
* runtime/linux/task_finder2.c: Ditto.
* runtime/transport/control.c: Ditto.
* runtime/transport/transport.c: Ditto.
* runtime/linux/autoconf-uidgid.c: New autoconf test.
* buildrun.cxx (compile_pass): Add STAPCONF_LINUX_UIDGID_H autoconf test.
* runtime/procfs.c: Include uidgid_compatibility.h.
* runtime/proc_fs_compatibility.h: Move KUIDT_INIT()/KGIDT_INIT() macros
  to uidgid_compatibility.h.
* runtime/transport/debugfs.c: Use KUIDT_INIT/KGIDT_INIT macros.
* runtime/transport/relay_v2.c: Ditto
* runtime/uidgid_compatibility.h: New file.