Settings in user_config.pri are overridden by those specified at the command line when calling qmake.
Also updated the README and user_config.pri.dist to be a little more clear about specifying these other options.

Also fixed some code in QGCPX4VehicleConfig to remove unnecessary DialogBare references.

Manual override through DISABLE_SPEECH now works on all platforms.

Makes sure all Windows code interfaces nicely with Qt. Also required
for utils and qupgrade libraries to compile.

It can now be manually disabled.

Can now be disabled by the DISABLE_KINECT define.
Also better output for users when running qmake.

Added documentation and clarified messages to the user.

This feature can be enabled at compile-time and documentation has been added to the README.

Replaced by /libs/serialport

Replaced by /libs/serialport.

Reduced it to folder descriptions and important files.

Separated into logical steps.
Made optional and required steps explicit.
Added instructions for Fedora.

XBee support can now be disabled by defining DISABLE_XBEE.
Details on why XBee support is disabled are now output.

Speech synthesis support can now be disabled (DEFINES+=DISABLE_SPEECH)
Speech synthesis dependencies are now checked before enabling.
When support cannot be enabled, the user is now notified.

MAVLink dialects can now be specified as a list, so multiple dialects can be compiled in simultaneously (may result in conflicts between dialects).
MAVLink dialects are checked for existance before support is added.
Users are notified of which dialects are used and which cannot be added and why.
The README now has info about specifying MAVLink dialects.

MAVLink dialects can now be specified as a list, so multiple dialects can be compiled in simultaneously (may result in conflicts between dialects).
MAVLink dialects are checked for existance before support is added.
Users are notified of which dialects are used and which cannot be added and why.
The README now has info about specifying MAVLink dialects.

Now properly checks for if QUpgrade submodule has been cloned.
Allows for disabled QUpgrade compilation.
Altered some code so that compiling without the QUpgrade module could
succeed.
Updated README about QUpgrade submodule.

flightgear HIL: also use default Scenery directory besides terrasync

Warnings fixes

Add libudev-dev to linux build requirements

This removes a race condition between both qwt and qt against math.h on
windows with _USE_MATH_DEFINES set. If math.h comes after qwt or qt
math headers the math defines will be redefined. Really nasty to track
down and ordering problems. So instead I just removed using math
defines on windows and fall back to asin definition of M_PI_2. This
will have some slight perf impact since it calls function instead of
using constant. But I doubt on any of today’s machine it really makes a
difference.

Number of warnings is low enough now to let them come through. Lowered
Windows warning level the /W3 to be more consistent with OSX/Linux
level of warnings. Removed /WX from Windows build. I’ll put it back
once everything is cleaned up.

Conflicts:
	src/comm/QGCFlightGearLink.cc