remove constructors from list of symbols, don't copy type and constructor symbols for bem_types and bem_constructors

remove BEAnnotateTypeNode and BEAttributeTypeNode, replace BETypeVar0TypeNode, BETypeVarNTypeNode and BENormalTypeNode by BEVar0TypeNode, BEVarNTypeNode and BESymbolTypeNode

remove struct flat_type, replace fields type_lhs by type_symbol and type_attribute, remove BEFlatType, adjust BEAbstractType, replace BEAlgebraicType, BEExtendableAlgebraicType and BERecordType by BEDefineAlgebraicType, BEDefineExtensibleAlgebraicType and BEDefineRecordType, add constructor index argument to BEDefineRecordType and pass TypeArgP instead of TypeNodeP to remove hack in this function and BEConstructorSymbol

replace BENodeDef and BENodeDefs by BENodeDefList, replace BEStrictNodeId and BEStrictNodeIds by BEStrictNodeIdList, replace BEConstructor and BEConstructors by BEConstructorList, replace BEField and BEFields by BEFieldList, replace BEString and BEStrings by BEStringList, replace BECodeParameter and BECodeParameters by BECodeParameterList, replace BENodeIdListElem and BENodeIds by BENodeIdList

prevent unnecessary scanning of abc files: fix test to only scan abc file of a system module if the strict entry of a function is called

remove type variable names in the backend, because they are not used: replace contents_tv by contents_tv_argument_n, remove struct type_var, replace functions BEVarTypeNode and BENumberedVarTypeNode by BETypeVar0TypeNode and BETypeVarNTypeNode (without type variable name), remove functions BETypeVar, BENumberedTypeVar and NewTypeVar

remove unused types BETypeVarListP, BEAttributeKindList and AttributeKindList, functions BENoTypeVars, BENoAttributeKinds and last argument of function BEFlatType in backend

remove unused type BEUniVarEquations, function BENoUniVarEquations and argument attributeEquations of function BETypeAlt in backend

remove unused functions BEAttributeKind, BEAttributeKinds, BEUniVarEquationsList and BEUniVarEquation and type TypeVarList from backend

remove typeVarList argument of BEFlatType (use BENoTypeVars), remove calls to BEAddForAllTypeVariables (that should have been removed already by a previous commit)

add substitute_special to module expand_types, extended version of substitute that also yields types that cannot be simplified by simplifyAndCheckTypeApplication, used in function instantiateTypes in module check, that generates specialized types, to be able to report errors for incorrect specialization of not kind * type variables with basic or function types (simplifyAndCheckTypeApplication cannot generate an incorrect type in this case, because type Type has no representation for these types)