I'm pretty sure this is an FP: ([ -f /usr/include/file.h ]), tho that's not a fact.
If you want to be 100 percent sure you could sha1sum your file(s) and ask one of the developers to verify it. I mean, that's the proper way I guess since they don't tack sha1/md5sums or gpg sigs onto their tarballs. If you've got Aide, Samhain or Tripwire installed and maintained the database the right way, I guess you can go for 100 percent minus some calculated risks.
I find this "Showtee" stuff kinda funny, jus like the RHSharpe one. There's only
one reference on the 'web and I've still gotta find sources for both "in the wild".