Initial work for Mantis 1197: Changing NUM_ATTR_BYTES produces crashy Glulx code

I have defined the symbols GOBJFIELD_CHAIN, GOBJFIELD_NAME, GOBJFIELD_PROPTAB,
GOBJFIELD_PARENT, GOBJFIELD_SIBLING, GOBJFIELD_CHILD. (Both as C macros
and Inform constants.) These are derived from NUM_ATTR_BYTES, which is
normally 7 for Glulx but can be increased to permit more attributes.

Many hardwired constants in the compiler and veneer code have been
replaced with these symbols.