AP_Logger: remove short-filename compatability code

[peterbarker]

We used to produce files hwih looked like log1.BIN. We moved to 00000001.BIN instead so things collate.

This code allowed the autopilot to return data from SD cards which had old logs on them.

[peterbarker]

Has been flight-tested on my Bixler

[peterbarker]

Board               AP_Periph  blimp  bootloader  copter  heli  iofirmware  plane  rover  sub
Durandal                       0      *           -8      -8                0      0      -8
Hitec-Airspeed      *                                                                     
KakuteH7-bdshot                -96    *           -96     -96               -96    -96    -96
MatekF405                      -96    *           -96     -96               -96    -96    -96
Pixhawk1-1M-bdshot             -96                -96     -96               -96    -96    -96
f103-QiotekPeriph   *                                                                     
f303-Universal      *                                                                     
iomcu                                                           *                         
revo-mini                      *      *           *       *                 *      *      *
skyviper-v2450                                    *