* harbour/include/hbdefs.h
+ added HB_VMUINT_MAX macro
* harbour/src/vm/hvm.c
* harbour/src/vm/itemapi.c
% use conditional #if compilation for code which depends on
HB_SIZE range. It should eliminate dummy code and pacify
warnings in some compilers.
NOTE: do not forget to update such #if conditions when we
switch to signed HB_SIZE type.