Refactor the destruction of the objects

[rseac]

Description

The destruction of objects with Matchers and SystemCClang should be revisited. It seems that the destruction of dynamically objects are not done properly.

[rseac]

The current design creates an incomplete ModuleDecl in Matchers. The ports are populated there. Then, for each instance that is recognized, a new ModuleDecl is created, and information from the incomplete ModuleDecl is copied into the new instance-specific ModuleDecl. When deleting an instance of ModuleDecl, we have to be careful. This is because we do not want to delete the instance-specific ModuleDecl, which has structures with pointers in it (PortDecl), and then delete the incomplete ModuleDecl because the latter will cause a double free memory error. This is because the deletion of the instance-specific ModuleDecl will free the objects identified in the incomplete ModuleDecl.

The current solution is to clear the information for the instance-specific ModuleDecl before deleting it. Then, the deletion of the incomplete ModuleDecl will free the other objects such as PortDecl.
clearOnlyGlobal does exactly this.