Object.constants includes :fatal

[eregon]

Found by @fniephaus

And so Object.constants.collect { |x| Object.const_get x } fails with wrong constant name fatal.

We should filter out constants with a lowercase name for Module#constants.

Avoiding attaching fatal as a constant of Object doesn't seem a proper fix because I think it can be queried from C exts, and on CRuby (on TruffleRuby too) there are also namespaced lowercase constants:

$ ruby -rstringio -e 'p StringIO.ancestors'
[StringIO, IO::generic_writable, IO::generic_readable, Enumerable, Data, Object, Kernel, BasicObject]

@bjfish Could you fix it?

[bjfish]

This is fixed at: 336721f