JSVV - Variable definition segment

Update part of JCL setup for promptable variables.

Table 1. JSVV Control Block
Offsets        
Dec Hex Type Len Name Description
0 (0) STRUCTURE 53 JSVV PROMPTABLE VARIABLES
0 (0) CHARACTER 8 JSVVNAME VARIABLE NAME
8 (8) CHARACTER 44 JSVVVALUE VALUE SET OR DEFAULT VALUE
52 (34) CHARACTER 1 JSVVTYPE USAGE TYPE (%|&|?)