Turn Data Constructors with constant members into constants

When all arguments of a Data Constructor are constants, the created
object will also be a constant.  For now this is only tracked for
closures without arguments and helps to avoid some allocations when
records for interfaces are created. (As they only contain funtion
pointers without arguments.)

[refactor] Codegen: use simpler state modification methods

Ensure static closure objects are properly aligned

[refactor] Remove unused import

[refactor] Get rid of `Reg RVal` usage in builtins, make sure all builtins return a value

Extract closure handling code into separate module

Turn closures without arguments into constants

If a "closure" object is created that doesn't capture any arguments, we
can use a statically allocated object (constant) instead of dynamically
allocating.  This greatly reduces allocations in most non-trivial code.

[refactor] Remove obsolete scratch file

[refactor] Extract string handling functions into separate module

[refactor] Remove last traces of pervasive `i`

[refactor] (Almost) get rid of omnipresent `i` for constant naming

[refactor] Add new modules to CMakeLists

[refactor] Extract `Integer` related functions into separate module

[refactor] Extract %extern primitives and foreign redirect map

[refactor] Move more casts into genericCast, simplify

[refactor] Move builtins onto their own module

[refactor] Move object asserts into Object module

[refactor] Get rid of handcrafted object headers

Fix showSep implementation in Data.Utils

[refactor] Extract more generic stuff from GenLLVMIR into submodules