ctags: Use C99 bool instead of defining our own

Use stdbool.h definitions instead of defining non-standard ones.

Signed-off-by: Collin Funk <collin.funk1@gmail.com>

Reviewed by: markj
MFC after: 2 weeks
Pull Request: https://github.com/freebsd/freebsd-src/pull/1107

(cherry picked from commit 87b0195ace1a71a1a07244890be3aaef72e1ffcd)