Remove unneeded art::Unit member functions

Remove ~Unit to avoid a build failure after libc++ upgrade:

art/cmdline/unit.h:29:3: error: definition of implicit copy assignment operator for 'Unit' is deprecated because it has a user-provided destructor [-Werror,-Wdeprecated-copy-with-user-provided-dtor]

(Perhaps std::vector changed to use assignment instead of a copy ctor.)

Also remove the Unit() default ctor, because it's unnecessary, and
Valgrind support has been deprecated for years now. Similarly, remove
the explicitly-defaulted copy ctor. It can be defined implicitly (i.e.
following the C++ "rule of zero").

Bug: http://b/175635923
Test: treehugger
Change-Id: Iefd41dad5b88361104ab159549058daa3b895612
1 file changed