[Orc] Remove the OwnedModules list from OrcMCJITReplacement and use

ExecutionEngine's Modules list instead.

This makes the owned modules visibile to ExecutionEngine. In particular,
it is required for ExecutionEngine::runStaticConstructorsAndDestructors to
work.

Regression tests for Orc (which test this issue) will be committed shortly.

llvm-svn: 227779