AP_Math: Using const references in matrix3

Signed-off-by: Daniel Frenzel <dgdanielf@gmail.com>
AP_PerfMon: removed unused blocking_writes

Signed-off-by: Daniel Frenzel <dgdanielf@gmail.com>
AP_GPS: removed wrong reassignment of msec

Signed-off-by: Daniel Frenzel <dgdanielf@gmail.com>
AP_Mission: Consecutive return, break, continue, goto or throw statements are unnecessary.

Signed-off-by: Daniel Frenzel <dgdanielf@gmail.com>
AP_Param: signed/unsigned conversion

Signed-off-by: Daniel Frenzel <dgdanielf@gmail.com>
DataFlash: Delete unused BufferRead function

Signed-off-by: Daniel Frenzel <dgdanielf@gmail.com>
DataFlash: removed more unusued BufferRead functions
AP_PerfMon: removed unusued commented code
GCS_MAVLink: fixed example sketch builds