Fix CodeGen assert failure for bounds-safe interfaces

[kkjeer]

Fixes #861

This PR fixes a type-related assert that failed during code generation. The assertion was that the subexpression of an LValueToRValue cast had the same unqualified type as the destination type. However, this failed for cases involving bounds-safe interfaces. For example:

_Checked unsigned f(const unsigned char *cp : count(1))
{
    return cp[0];
}

Since cp has a bounds-safe interface type of _Array_ptr<unsigned char>, there is an implicit cast (_Array_ptr<const unsigned char>)cp in the subexpression of the cast LValueToRValue((_Array_ptr<const unsigned char>)cp). The destination type of the LValueToRValue cast is unsigned char *. This caused the CodeGen assert hasSameUnqualifiedType(_Array_ptr<const unsigned char>, unsigned char *) to fail.

This PR introduces a new method hasSameUnqualifiedUncheckedType which returns true if two types are the same, ignoring qualifiers and the checkedness of any pointer types. hasSameUnqualifiedUncheckedType(_Array_ptr<const unsigned char>, unsigned char *) returns true.

Testing:

• Passed manual testing on Windows.
• Passed automated testing on Windows/Linux.

[mgrang]

LGTM.

[dtarditi]

LGTM also.