WIP SI-7518 Position retention for inlined code

The inliner was positioning all inlined instructions
at the method call (`targetPos). This makes debugging
of code compiled under `-optimize` difficult.

This commit retains the original position of the
inlined instruction if it is in the same source file
as the method call.

TODO: This still seems aribtrary. What was the intent
of using `targetPos`? Should we expand the above to
any source position? What about code inlined from class
files: should they be treated any differently?