RangeStatement validation in CASE

[99NIMI]

found in OSCAT

CASE DAYS_IN_MONTH OF
  32..60	:	DAYS_IN_MONTH := 29;
  92..121 :	DAYS_IN_MONTH := 30;
  153..182:	DAYS_IN_MONTH := 30;
  245..274:	DAYS_IN_MONTH := 30;
  306..335:	DAYS_IN_MONTH := 30;
ELSE
  DAYS_IN_MONTH := 31;
END_CASE;

these should be valid cases but currently we will get the following error

error: Cannot resolve constant: RangeStatement {
    start: LiteralInteger {
        value: 32,
    },
    end: LiteralInteger {
        value: 60,
    },
}. Non constant variables are not supported in case conditions

for RangeStatements we need to visit the start and end statement and check if constant