Address some MacOS build items from #50

[jnardone]

This covers a number of issues: 1) enables logging sink on MacOS 2) fixes "const" error and "override" warnings 3) excludes MacOS from "memcpy" compat lib

There is one warning I'm not sure how to fix, because I'm not sure what (if anything) to do for the states listed:

[ 95%] Building CXX object src/client/CMakeFiles/ssf.dir/ssf.cpp.o
/Users/jnardone/src/t/ssf/src/client/ssf.cpp:112:13: warning: enumeration values 'kInitialized',
      'kServerNotSupported', and 'kRunning' not handled in switch [-Wswitch]
    switch (status) {
            ^
/Users/jnardone/src/t/ssf/src/client/ssf.cpp:112:13: note: add missing switch cases
    switch (status) {
            ^
1 warning generated.

[securesocketfunneling]

Thanks for your PR, it is really appreciated!

I would like to add minor fixes to your proposal. Would you mind applying the following patch? It provides fixes for ssf.cpp and ssfd compilation warnings. It also improves the memcpy tweak management (mostly related to GCC and GLIBC versions). The latter is not perfect but it should do the trick for now.

Could you also check that your OSX build is still fine?

Thank you

[jnardone]

Looks good; applied and pushed (built fine locally)

[securesocketfunneling]

Thanks for your contribution :-)