Global revision of message severity values.
Required also change to the low priority function gcs_send_text_fmt()
on GCS_Mavlink.cpp to disable the automatic setting of priority on
messages sent by this function
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.