fix bug in fusion: store type information of let bound variables when transforming case (let ) to let (case )

change type PredefinedSymbolsData  to !{psd_predefs_a :: !{#PredefinedSymbol}} (an extra field will be added later)

replace type PredefinedSymbols by type PredefinedSymbolsData:==PredefinedSymbols (to be changed later)

remove some unused functions

this may occur if the result type of a synonym type or newtype is a type variabele,
this should be fixed

	

use synonym type AttrVarHeap instead of Heap AttrVarInfo

by code that checks if it is an ExtensibleAlgType and whether the root attribute and arity are the same

reorder some function arguments,
don't call getBelongingSymbols again in get_nth_belonging_decl

modules_explicit_imports, component_mods and path to functions

specialize functions search_symbol and search_imported_symbol for searching a symbol or belongings of a symbol,
the specialize functions for belongings are search_belonging_symbol and search_imported_symbol_and_belonging,
remove cUndef, implies and stupid_ident

rename function try_children to search_symbol_in_imports,
inline local function continue

add some function types

replace fields icl_import and icl_qualified_imports by icl_imported_instances,
add type GlobalInstanceIndex,
add function collect_imported_instances to module explicitimports,
remove unused Position from si_qualified_explicit

add type GlobalInstanceIndex,
add function collect_imported_instances to module explicitimports,
remove unused Position from si_qualified_explicit

from module checksupport to explicitimports,
make ExplImpInfo abstract and don't export DeclaringModulesSet and DeclarationInfo

[ReferenceCount] usually consists of many RC_Unused,
these lists are replaced by a single ReferenceCountsAllUnused

add types in TC contexts of constructors with dictionaries to the type environment of dynamic types (at runtime).
to fix for example:

:: T = E.a b: A (a -> b) & TC a & TC b

tToDyn :: !T -> Dynamic
tToDyn (A x) = toDyn x

toDyn :: a -> Dynamic | TC a
toDyn a = dynamic a