style: use = default for empty destructors

[TingleDinkle]

Small style cleanup — use = default for empty destructors in matching code.

Changes

• mapObjectLink.h: ~ObjectLink() {} → = default
• actBaseProcJob.h: ~BaseProcJobLists() { ; } → = default

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This change is 

[leoetlino]

~BaseProcJobLists() { ; } and ~BaseProcJobLists() {} are not equivalent - the former inhibits some optimisations because older versions of Clang checked whether the destructor function body was literally empty instead of checking if the body was functionally empty

The mapObjectLink change should be semantically equivalent but unfortunately that appears to change codegen

[TingleDinkle]

~BaseProcJobLists() { ; } and ~BaseProcJobLists() {} are not equivalent - the former inhibits some optimisations because older versions of Clang checked whether the destructor function body was literally empty instead of checking if the body was functionally empty

The mapObjectLink change should be semantically equivalent but unfortunately that appears to change codegen

Fascinating, I didn't realize the older Clang compiler was that literal about the stray semicolon in { ; }! Thanks for explaining the codegen shift, it makes total sense now. I was wondering since yesterday about this