Draft: DO NOT MERGE: build-aux,qmi-codegen: fix introspection of complex array types

Make structs always heap allocated, even when in arrays (e.g. so that the arrays would store the pointer of each struct, not the struct itself).

Also register the structs as boxed types with full copy() and free() methods so that introspection can work correctly on them.

And then, use GPtrArray instead of GArray in types that require heap allocation (e.g. arrays of arrays, arrays of strings or arrays of structs).

This change BREAKS API BADLY.

Fixes #83 (closed)