Check bounds declarations for pointers to constant-sized data for a subset of expressions

[dtarditi]

This work item is to check bounds declarations to pointers to constant-sized data, where the bounds have the form bounds(_x_ + _const1_, _y_ + const2).   We will check bounds declarations for a subset of expressions that are useful for creating ptr-typed values.  These include:

• address-of operators
• uses of unchecked arrays with known dimensions
• uses of unchecked arrays with known dimensions that are not parameters
• function calls.  For function calls, we will need to substitute constant argument  expressions for parameter variables occurring in the return count.  We will then need to determine whether the resulting expression is a constant-expression.
• casts

It also includes checking bounds at

• Simple assignments
• Function calls

[dtarditi]

Work item #412 implements this feature. Work items #416 and #413 cover follow up work.