PKG_OZCR, Register OZ call substitution

rst $08, defw $1e0f


IN:	DE=OZ call ID to be substituted
	BC=package call ID to use
OUT(success):
	Fc=0
OUT(failure):
	Fc=1
	A=rc_pnf, call substitution table not available
	A=rc_room, substitution already in place for this call
	A=rc_bad, invalid OZ call ID

Registers changed after return:
  ..BC..HL/IXIY same
  AF..DE../.... different

Bugs:
	This call should only be used with Packages v1.12 and higher, due to
	a bug in the call substitution system in v1.11.

Notes:
	This call does not test validity of package call; but substitution
	will be ignored if invalid, or package not available
	On entry to a substituted call, the original binding of segment 3
        is only available at SP+11, *not* at SP+3
	To force standard OZ call to be used, restore all registers and
	exit with Fc=1 and A=rc_pnf
