DebugInfo: Create abstract function definitions even when concrete definitions...

DebugInfo: Create abstract function definitions even when concrete definitions preceed inline definitions.

After much puppetry, here's the major piece of the work to ensure that
even when a concrete definition preceeds all inline definitions, an
abstract definition is still created and referenced from both concrete
and inline definitions.

Variables are still broken in this case (see comment in
dbg-value-inlined-parameter.ll test case) and will be addressed in
follow up work.

llvm-svn: 209677