New rule: Identifiers should not shadow compiler intrinsics

[fourls]

Prerequisites

• [X] This rule has not already been suggested.
• [X] This should be a new rule, not an improvement to an existing rule.
• [X] This rule would be generally useful, not specific to my code or setup.

Suggested rule title

Identifiers should not shadow compiler intrinsics

Rule description

This rule forbids identifiers that share a name with a compiler intrinsic.

This would include a configurable whitelist for acceptable intrinsics to shadow.

Rationale

This can be confusing for a number of reasons:

• Compiler intrinsics have special "magic" behaviour that is not replaceable if it is shadowed (except by prefacing System.)
• Intrinsics are almost always expected to be the intrinsic value (e.g. Break, Continue, True)
• The Delphi IDE adds decorators for certain intrinsics, and does not differentiate between the intrinsic and a shadowing identifier of the same name

[cirras]

Couldn't agree more, let's do it.