gccrs: Fix issues around PartialEq Eq Ord Partial Ord

gccrs: Fix issues around PartialEq Eq Ord Partial Ord

There is still an issue with derive on PartialOrd but this adds good tests
and fixes a bug we had handling the default Rhs = Self generic type param
substitutions on the comparison traits.

gcc/rust/ChangeLog:

	* typecheck/rust-tyty.cc (ParamType::handle_substitions): make this consistent

gcc/testsuite/ChangeLog:

	* rust/compile/bug-with-default-generic.rs: New test.
	* rust/execute/torture/partial-eq-1.rs: New test.
	* rust/execute/torture/partial-eq-2.rs: New test.
	* rust/execute/torture/partial-eq-3.rs: New test.
	* rust/execute/torture/partial-eq-4.rs: New test.
	* rust/execute/torture/partial-ord-1.rs: New test.
	* rust/execute/torture/partial-ord-2.rs: New test.
	* rust/execute/torture/partial-ord-3.rs: New test.
	* rust/execute/torture/partial-ord-4.rs: New test.
	* rust/execute/torture/partial-ord-5.rs: New test.

Signed-off-by: Philip Herron <herron.philip@googlemail.com>