[SR-341] Make test/SIL/Parser/witness_with_inherited_gp.sil not depend on stdlib and remove XFAIL

[gottesmm]

Previous ID	SR-341
Radar	None
Original Reporter	@gottesmm
Type	Bug

Additional Detail from JIRA

Votes	0
Component/s	Compiler
Labels	Bug, StarterBug
Assignee	None
Priority	Medium

md5: 8e2872d7bfc9887a64565cb007fd1902

Issue Description:

From Dmitri some months ago:

The test test/SIL/Parser/witness_with_inherited_gp.sil depends on the standard library implementation details (underscored protocols). It should define its own version of all protocols to ensure that it continues to test what was intended.

I'm making changes to these underscored protocols, the test broke, and I don't know how to update it properly.

I disabled the test.

[Dante-Broggi]

The test is still XFAIL'ed on master, as of this edit.