inline new mixin methods

[lrytz]

trait T { @inline def f = 1 } } // note that f is not final
class C extends T

bfore nuke-impl-classes, the mixin f in C is def f = T$class.f(this), which is inlined.

with default methods the mixin becomes def f = super.f and is currently not inlined, even though it could (INVOKESPECIAL).

Note that this also causes an inliner warning (T::f()I is annotated @inline but cannot be inlined: the method is not final and may be overridden)

[lrytz]

Another issue: module accessors in traits were effectivelyFinal before the patch, now not anymore. Need to investigate, see ScalaInlineInfoTest.