identification of platform paths is not done in a cross-platform way

[JonathanAldrich]

ModuleDeclaration.isPlatformPath() uses a unix-specific pattern; it should be made to work on Windows and Unix.

Unfortunately, when the function returns true on unix, if type Stdout is ascribed to the stdout module, there is an error. So fixing the bug above and adding this as a test case will in fact trigger an underlying error (whose cause is not yet identified).

[JonathanAldrich]

Replaced the pattern with one that works in a cross-platform way.

The pattern is still limited; it doesn't detect files in subdirectories of the platform directory. Still need to fix this part, but it triggers another bug so I'm postponing the generalization for now.