Merge changes from topic 'vndk-def-tool'

* changes:
  vndk-def: Cleanup ELF linker test cases.
  vndk-def: Implement ELF resolver.
  vndk-def: Fix python2 unittest.
  vndk-def: Separate DT_RUNPATH with semicolon.
  vndk-def: Process import symbols.
  vndk-def: Rename Graph to ELFLinker.
  vndk-def: Refactor exported symbols.