Adds arrays and structs support for assigns clauses

Assigns clauses should handle multiple targets.
Previously, it only supported identifiers (e.g., variable `x`)
and dereferenced pointers (e.g., *myPtr). So, we expand its support to
also handle members of a struct (e.g. `myStruct.someMember` or
`myStructPtr->otherMember`) and array ranges (e.g. `myArr[5, lastIdx]`).

Signed-off-by: Felipe R. Monteiro <[email protected]>

Author: feliperodri