Give proper error when trying to instantiate Module

[wooster0]

Fixes #3885

Now this:

module Foo
  def initialize
  end
end
Foo.new

gives:

Error in test.cr:5: instantiating 'Foo:Module#new()'

Foo.new
    ^~~

in test.cr:2: cannot instantiate Foo:Module

  def initialize
  ^

instead of:

Error in line 5: instantiating 'Foo:Module#new()'

in line 2: undefined local variable or method 'allocate'

[straight-shoota]

I'm not sure this is a good change. allocate could just be a regular method on a module and could be called as suche. The error message is at least misleading in a case where the method was just not defined - because some include is missing, or the def is mispelled for example. This could very well be a valid call even on a module.

module Foo
  def self.allocate
  end
end

Foo.allocate`

Failing to call a method allocate on a module doesn't mean you're trying to instantiate it.

I'd leave the error message as is and maybe add a note about being unable to instantiate a module.

[jhass]

Perhaps we rather should make sure the call to .new already fails unless it's defined explicitly

[straight-shoota]

@r00ster91 Can you change this to add a note to the original error instead? @jhass's suggestion can come later.

[RX14]

Specs need updating

[asterite]

This condition should check if onwer is a MetaclassType and owner.instance_type.module?

The current check reads well but makes no sense because a MetaclassType inherits from ModuleType. It just happens to work because the only metaclasses that don't have an allocate are modules, though I think this check will also trigger for enums