The PSTR is already define as a NOP for all supported platforms. It's
only needed for AVR so here we remove all the uses throughout the
codebase.
This was automated with a simple python script so it also converts
places which spans to multiple lines, removing the matching parentheses.
AVR-specific places were not changed.
The EKF failsafe now captures all failures that could lead to a bad
position including GPS glitches and a bad compass meaning we do not need
this protection in the main flight code.
Caio Marcelo de Oliveira Filho
Lucas De Marchi
squilter
Andrew Tridgell
Robert Lefebvre
Randy Mackay