Remove isnan() and isinf() templates from QGC.h for Windows builds, this
generates errors (already defined in math.h).

Add debug output for when voice initialization fails on Windows

Removed or annotated existing commented-out code

Clean up logic for saying emergency text.

Previous code didn't properly check for if speech was enabled.

Some functionality was lost, will need to be fixed in a later commit.

To include OpenGL primitives, we include the QtOpenGL header instead, which has all the platform-specific includes taken care of for us.

Also added selection from tree view for downloading