Allow overriding the types default initializer when using aliases/ref-initialization

[mhasel]

In the current implementation of the initializer functions, data types are unconditionally initialized with their declared type-initializer. If a new initializer is set for an instance, it is currently not initialized correctly. We should adapt the implementation to allow non-default-initializers in init-functions (fb: foo := (s1 := REF(ps)); such that __init_foo initializes foo.s1 with the address of ps instead of the default type initializer).