Keeping it Real, add Gmprat::Str, Gmprat::Log10

Fixed* all those horrible compile errors.
View can now use VReal and Path can now use PReal
	and at the moment they are Gmprat unless the quadtree is enabled.

For Gmprat::Log10 there are problems.

Using: log(a/b) = log(a) - log(b)
       log(a*b) = log(a) + log(b)

Unfortunately mpz_div_ui quickly becomes a massive performance issue.
Even when well within the range of IEEE singles.

Need to rewrite Gmprat::Log10 but may as well commit since it works* slowly at least.