Removed a bunch of empty destructors

Their declaration violates the 'rule of 3' and was
causing compiler warnings with clang's -Wdeprecated
in C++11.

Change-Id: I959d582deea4ceccc69684be32dccd3521f54807
Merge topic 'rule-of-three' into master

9e42e0e1 Removed a bunch of empty destructors