Enable cast warnings in gcc and clang and always treat warnings as
errors.
GetWordCount now returns std::size_t for simplicity and the word count
is asserted and casted in WordCount (now called CalculateTotalWords.
Silence warnings.
Previously this wasn't utilizing any of the compiler flags, meaning it
wasn't applying any of the specified warnings.
Since applying the warnings to the target, this uncovered a few warning
cases, such as shadowing class variables on MSVC, etc, which have been fixed.
By taking the std::string by value in the constructor, this allows for
certain situations where copies can be elided entirely (when moving an
instance into the constructor)
e.g.
std::string var = ...
...
... = LiteralString(std::move(var)) // Or whatever other initialization
// is done.
No copy will be done in this case, the move transfers it into the
constructor, and then the move within the initializer list transfers it
into the member variable.
tl;dr: This allows the calling code to potentially construct less
std::string instances by allowing moving into the parameters themselves.
