Type-checking pointer offsets completely

[Mesabloo]

• This function handles pointers to simply sized types (pointers of the form *t where t is not a structure type), but does not handle stack pointers offsets.
  https://github.com/zilch-lang/nsc/blob/4c1fcc20dcaef6aebb3fe0c2532722efdda5da58/lib/nsc-typechecker/src/Language/NStar/Typechecker/Instructions.hs#L338-L350

• pop is only type-checked when the destination expression is a register.
  https://github.com/zilch-lang/nsc/blob/4c1fcc20dcaef6aebb3fe0c2532722efdda5da58/lib/nsc-typechecker/src/Language/NStar/Typechecker/Instructions.hs#L309-L317

• mov is only type-checked when the destination expression is a register, but should work for any kind of source expression (as long as the first quoted code works for any pointer offset).
  https://github.com/zilch-lang/nsc/blob/4c1fcc20dcaef6aebb3fe0c2532722efdda5da58/lib/nsc-typechecker/src/Language/NStar/Typechecker/Instructions.hs#L115-L129

[Mesabloo]

Closed in favor of #50, which also adds additional functionalities.