Scan geometry control

The scan geometry has been introduced in GEANT version 3.15 with the idea of developing a general parametrisation scheme. While the scan geometry can already be built, the parametrisation scheme has not yet been developed, so the following data records have to be considered as a forward compatibility feature.

KEY	N	I	VAR	Short description	COMMON	GINIT
PCUT	6	M	4lparametrisation control
		IPARAM	parametrisation flag	/GCPARM/	0
		PCUTGA	threshold for gammas	/GCPARM/	0
		PCUTEL	threshold for e-e+	/GCPARM/	0
		PCUTNE	threshold for neutral hadrons	/GCPARM/	0
		PCUTHA	threshold for charged hadrons	/GCPARM/	0
		PCUTMU	threshold for muons	/GCPARM/	0
PNUM	2	I	4lparametrisation stack size
		MPSTAK	size of the parametrisation stack	/GCPARM/	1000
		NPGENE	number of pseudo-particles generated	/GCPARM/	20
SCAN	8	M	4lscan geometry control
		SCANFL	scan processing flag (LOGICAL)	/GCSCAN/	.FALSE.
		NPHI	number of divisions in $\phi$	/GCSCAN/	90
		PHIMIN	minimum value of $\phi$	/GCSCAN/	0
		PHIMAX	maximum value of $\phi$	/GCSCAN/	360
		NTETA	number of divisions in $\theta$	/GCSCAN/	90
		TETMIN	minimum value of $\theta$	/GCSCAN/	0
		TETMAX	maximum value of $\theta$	/GCSCAN/	180
		MODTET	type of $\theta$ division	/GCSCAN/	1
SCAL	32	M	ISLIST	list of volumes to be scanned	/GCSCAN/	Blank

KEY	N	I	VAR	Short description	COMMON	GINIT
SCAP	6	R	4lscan parameters
		VX	scan vertex X coordinate	/GCSCAN/	0
		VY	scan vertex Y coordinate	/GCSCAN/	0
		VZ	scan vertex Z coordinate	/GCSCAN/	0
		FACTX0	scale factor for SX0	/GCSCAN/	100
		FACTL	scale factor for SL	/GCSCAN/	1000
		FACTR	scale factor for R	/GCSCAN/	100