Get rid of some includes, and use "u_int8_t" and "u_int16_t" in packet

layout definitions, as per Alfredo Andrés's suggestion.

Don't use expressions with side effects inside EXTRACT macros - the
arguments of those macros are used more than once, so the side-effects
(incrementing the pointer) occurs more than once, and they occur in a
sequence that may not be the same for all compilers.

When printing a UNIX time value, extract the value into a "time_t"
variable, and then pass a pointer to that variable to "ctime()", don't
cast the result of "EXTRACT_32BITS()" to a pointer.  Also, when printing
the result of "ctime()", print only the first 24 characters, so that the
newline at the end isn't printed.

Cast the first argument passed to "radius_attr_print()", and the
argument passed to the print function for an attribute, to "u_char *",
not "char *", as those routines expect a "u_char *".