linux speech synthesis: switch to eSpeak

Conflicts:
	QGCExternalLibs.pri
	src/GAudioOutput.cc
Re-enable the local 3D and Google Earth 3D views, needs testing
Not quite right yet
Added 2 kPA offset to pressure measurements to get HIL closer to real conditions
Fixed wrong location of offset constant
flightgear: add configurable barometer offset
Merge remote-tracking branch 'upstream/master' into espeak

Conflicts:
	QGCExternalLibs.pri
	src/GAudioOutput.cc
	src/GAudioOutput.h
remove alsa asound library dependency comment
fix merge errors and unused-variable error
Issue 535 fix
Merged master, fixed local 3D init
Added comment for sensor selection
Changes to allow msbuild to build installers

No idea why, but manipulating CONFIG inside the build file confuses
msbuild command line builds. Work fine if you build from the IDE!
Disable text output from GAudioOutput.
All it does is clutter the terminal and it's not doing anything anyways.
Merge pull request #546 from Susurrus/remove_beep

Disable text output from GAudioOutput.
Merge pull request #540 from mavlink/3dviews

3dviews
QGCMessageView: Extensive code cleanup and bug fixing.
Right-click menu works cleaner.
Coloring of output text is correct.
Output text now handles all severities of messages.
QGCMessageView: Added timestamps.
Google earth: Corrected #ifdef for Google Earth-specific code.
Message view: Forgot to remove debugging output.