[C++]: Simplify bool methods in codecs

[vdidenko]

Currently the C++code generator produces return statements like this:

return (m_actingVersion >= mdEntryTypeSinceVersion()) ? true : false;

(see the generated codecs for example: all lines in that file where true occurs).

Could it be simpler:

return m_actingVersion >= mdEntryTypeSinceVersion();

Is there a hidden meaning to this complication? If not, it is ready for a pull: vdidenko/simple-binary-encoding@94389b12920e632b17c5a5e70b4b0aa00ac061d3

[tmontgomery]

it should be simpler, yeah. Go ahead with a PR.