Ignore case for symbol table map entries
Allow boolean literals for write parameters
Various fixes to genArithmetic; disallow 'and'/'or' for numeric types,
fix integer/float division, disallow mod on floats
Fix NPE for undeclared identifiers 'type' reference
Fix NPE for undeclared identifier in variableIdentifier
Fix NPE in genReadStmt
Grammar doesn't include a colon in FunctionHeading; fix for
optionalFormalParameterList --> epsilon
Fix valid boolean operation check