Simple change to silence warnings, changes the offending enums to be
constexprs. There is still more cleanup work to update other enums;
this just addresses the ones causing compiler warnings
Port libtransmission to C++. This PR doesn't refactor everything to c++.
Its code changes are only what was necessary to compile and link as c++.
See libtransmission/README.md for details on how to submit modernization
patches!
Co-authored-by: Mike Gelfand <mikedld@mikedld.com>