Show altitude even when not in rotating frame.
Show vertical speed together with altitude.
Use parent frame for starports and only calculate altitude if close enough.
Fix frame confusion and some minor issues in altitude/vspeed calculations.
use static_cast when casting between void* and a specific pointer type

See this StackOverflow question:

http://stackoverflow.com/questions/310451/should-i-use-static-cast-or-reinterpret-cast-when-casting-a-void-to-whatever

But note that reinterpret_cast for this does work fine in practice, and is
defined to work fine in C++11 (assuming that change got through committee).

My reason for preferring static_cast is really that static_cast works,
so taking reinterpret_cast out of the big scary toolbox of C++ features
marked "use-at-your-own-risk", "here-be-dragons", is not necessary and
should therefore be avoided.
use static_cast when downcasting from Body* to a derived class

reinterpret_cast is incorrect for this purpose, and could result in
serious bugs.
Merge remote-tracking branch 'johnbartholomew/cleanup-reinterpret-cast'
Merge remote-tracking branch 'lwho/altitude_view'

Conflicts:
	src/WorldView.cpp