(svn r12871) [0.6] -Backport from trunk r12819, r12818, r12759:
- Fix: Inconsistent use of 8/15-bitness of NewGRF callback results with respect to TTDP's implementation of the specification (r12819, r12818, r12759)

Makefile*
bin/*
!bin/data/chars.grf
!bin/data/openttdd.grf
!bin/data/openttdw.grf
!bin/data/opntitle.grf
!bin/scenario/README
!bin/scripts*
config.*
objs/*
src/rev.cpp