Improved instructions for vxWorks build

Signed-off-by: Ian Bell <ian.h.bell@gmail.com>
Fixed https://github.com/ibell/coolprop/issues/87

Signed-off-by: Ian Bell <ian.h.bell@gmail.com>
Merged vxWorks changes

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

Conflicts:
	CoolProp/gitrevision.h

Fixed

Signed-off-by: Ian Bell <ian.h.bell@gmail.com>