Un-inlined definition of a constructor in z3++.h

[kix6lj]

There is a un-inlined constructor of constructor_list in z3++.h. When z3++.h is included in multiple sources, this causes a "multiple definition" error. Inline the definition should solve the problem.

[sjunges]

Just to confirm, I run into the same issue when linking against z3 with 4.10.1, but not with 4.9.1.

[ekilmer]

Relevant comment here about the same issue in vcpkg while building Triton 5b219aa#r79292178