Some small cleanup from the release of v4.2.4

Signed-off-by: Ian Bell <ian.h.bell@gmail.com>
Cleaned up some errors/warnings recommended by clang - still fails.

Signed-off-by: Ian Bell <ian.h.bell@gmail.com>
"Fixed" mysterious bug referenced in https://github.com/CoolProp/CoolProp/issues/86 .  Not at all clear why there was a problem in the first place. Might be a bug outside of CoolProp.

Signed-off-by: Ian Bell <ian.h.bell@gmail.com>
Merge branch 'master' of https://github.com/ibell/coolprop