Minor cleanup in various files

Changed 1 to true in a couple of places that I missed earlier.
-- Add SimpleMake makefile to build without needing autoconf, automake and
   friends.
-- countries.{h,c}: fix mismatch in array declaration and add const;
   remove superfluous array size; include header in C file so that
   mismatches can be caught by compiler.
-- udp-filter.h: remove explicit assignment of values since enums, by default
   start at 0 and increment by 1; add last member to track number of values.
-- udp-filter.c: use MAX_FILTER instead of manifest constant; remove
   superfluous variable num_predefined_filters; use bool type where appropriate;
   remove unused variable found_multiple_ips.
-- utils.c: include header in C file

Change-Id: Id47ec9a4e4855d43e632ea0d71ef83323a30413f