[trivial PATCH 11/22] [extern.h] eliminate build warnings

[Frank Cusack]

This applies to patches 11-16.

Having these be individual unrelated patches is very annoying.  It's
very difficult to review because the change in prototype is not in
the same change as the change to the functions.  So I haven't done
a thorough job, but for once I am going to blame the author instead
of my own laziness.

This just looks like churn to me.  You change the types of vars from
char to unsigned char, but then cast them back when they are used.

In at least 2 cases where I caught it, the change in var type is
incorrect and you are just making a trivial change without understanding
the effects other than to quiet the compiler on your system.

There may be at least one change that was correct, and that would only
have been the case if a radius structure member changed its signedness.
Because of the difficulty of reviewing the changes I'm not going
to try to go back and pick out where I thought that might have
been the case.

I have in the past been extremely diligent about not having any
compiler warnings so I'm surprised that rlm_otp is generating any
noise.  There must be one member in a radius struct somewhere that
changed and that is filtering down.

-frank