Prevent flips at high throttle

Conflicts:
	src/drivers/ardrone_interface/ardrone_motor_control.c
Make px_mkfw.py and px_upload.py compatible with both python 2.7 and 3.3
Allow mixer upload when PWM is on
respect NAV_TAKEOFF_ALT instead of using hardcoded default takeoff value
Merge pull request #374 from julianoes/hotfix_mixer

Allow mixer upload when PWM is on
multirotor_pos_control: added takeoff gap (hardcoded 3m), fixed code style
Added parameter NAV_TAKEOFF_GAP
Merge branch 'respect_takeoff_alt'
Set sane defaults for F330
v4 compatibility
Merge branch 'master' of github.com:PX4/Firmware
MAVLink workaround
Hotfix for USB: Starting MAVLink only on USB if connected. Needs rewrite of MAVLink and delay / retries for correct approach
Merge branch 'master' into python3_compat
Merge pull request #304 from julianoes/ardrone_fixes

Prevent flips at high throttle
Fix UART buf sizes so that MAVLink transfers are not corrupted for all serial ports intended for MAVLink
Reset baudrate after px4io update
Merge pull request #375 from julianoes/hotfix_px4io_uart

Reset baudrate after px4io update
Hotfix: Identified mavlink issue source, workaround, working on a fix
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