Assume the highest supported compiler version when a new compiler is released

[rlebeau]

In JEDI for example, when a new compiler version is released, jedi.inc defines various compiler directives (HAS_..., etc) from the highest supported compiler, thus easing compilation in new releases when non-breaking changes are not present.

Indy's IdCompilerDefines.inc does not define its HAS_... and ..._OR_ABOVE defines in new compiler versions, causing various compilation errors until IdCompilerDefines.inc is updated to recognize the new compilers. It should use a fallback, similar to how JEDI does.