Fix type-parameterized object methods.

[froystig]

See (XFAILed) run-pass/generic-obj.rs for sample testcase. A method that takes an argument whose type is a type-parameter of its enclosing object, e.g.

obj fooer[T]() { fn foo(T t) {} }

causes rustboot to get-element-pointer on something dynamically-sized during translation. Methods returning T to work fine, on the other hand.

[froystig]

Issue #92 was fixed with 25a38ee, which means that the above test now compiles. But now it segfaults at runtime instead. This appears to happen when the fooer.foo()'s arguments are dropped (can be made to happen earlier if a copy on a T occurs inside of fooer.foo()). This might be a bug in calling drop/copy glue, drop/copy glue itself, in the size calculations that take place right before either one of those), or in none of the above. Needs further investigation.

[froystig]

Adjust testcase to cover issue #91, which was actually fixed back in commit f02f9cb. Closed by 1a61fb8.