ctags: Use C99 bool instead of defining our own

[collinfunk]

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

[collinfunk]

Two of the style(9) failures are from the weird GETC macro. The others are because I did not add previously missing parentheses around return values. Should I amend or leave it for a different patch?

[bsdimp]

I'd match the existing style, so don't change the returns. The GETC stuff is a weird macro, and it's just a false positive, so it's good.

[bsdimp]

I think this is ready. I'll try to land it later today.

[collinfunk]

That should be all of them hopefully...

[markjdb]

Merged.