This patch supports the following checks for THREADPRIVATE Directive:

```
[5.1] 2.21.2 THREADPRIVATE Directive
A variable that appears in a threadprivate directive must be declared in
the scope of a module or have the SAVE attribute, either explicitly or
implicitly.
A variable that appears in a threadprivate directive must not be an
element of a common block or appear in an EQUIVALENCE statement.
```

This patch supports the following checks for DECLARE TARGET Directive:
```
[5.1] 2.14.7 Declare Target Directive
A variable that is part of another variable (as an array, structure
element or type parameter inquiry) cannot appear in a declare
target directive.
A variable that appears in a declare target directive must be declared
in the scope of a module or have the SAVE attribute, either explicitly
or implicitly.
A variable that appears in a declare target directive must not be an
element of a common block or appear in an EQUIVALENCE statement.
```

As Fortran 2018 standard [8.5.16] states, a variable, common block, or
procedure pointer declared in the scoping unit of a main program,
module, or submodule implicitly has the SAVE attribute, which may be
confirmed by explicit specification.

Reviewed By: kiranchandramohan

Differential Revision: https://reviews.llvm.org/D109864