Remove mystery-board 99

Marlin/boards.h

 #define BOARD_BAM_DICE_DUE      402  // 2PrintBeta BAM&DICE Due with STK drivers
 #define BOARD_BQ_ZUM_MEGA_3D    503  // bq ZUM Mega 3D
 
-#define BOARD_99                99   // This is in pins.h but...?
-
 #define MB(board) (MOTHERBOARD==BOARD_##board)
 
 #endif //__BOARDS_H

Marlin/pins.h

   #include "pins_MEGACONTROLLER.h"
 #elif MB(BQ_ZUM_MEGA_3D)
   #include "pins_BQ_ZUM_MEGA_3D.h"
-#elif MB(99)
-  #include "pins_99.h"
 #elif MB(AJ4P)
   #include "pins_AJ4P.h"
 #elif MB(MKS_13)

Marlin/pins_99.h

-/**
- * Marlin 3D Printer Firmware
- * Copyright (C) 2016 MarlinFirmware [https://github.com/MarlinFirmware/Marlin]
- *
- * Based on Sprinter and grbl.
- * Copyright (C) 2011 Camiel Gubbels / Erik van der Zalm
- *
- * This program is free software: you can redistribute it and/or modify
- * it under the terms of the GNU General Public License as published by
- * the Free Software Foundation, either version 3 of the License, or
- * (at your option) any later version.
- *
- * This program is distributed in the hope that it will be useful,
- * but WITHOUT ANY WARRANTY; without even the implied warranty of
- * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
- * GNU General Public License for more details.
- *
- * You should have received a copy of the GNU General Public License
- * along with this program.  If not, see <http://www.gnu.org/licenses/>.
- *
- */
-
-/**
- * Board 99 pin assignments
- */
-
-#define BOARD_NAME          "99 Unknown"
-
-//
-// Limit Switches
-//
-#define X_STOP_PIN         16
-#define Y_STOP_PIN         67
-#define Z_STOP_PIN         59
-
-//
-// Steppers
-//
-#define X_STEP_PIN          2
-#define X_DIR_PIN           3
-#define X_ENABLE_PIN       -1
-
-#define Y_STEP_PIN          5
-#define Y_DIR_PIN           6
-#define Y_ENABLE_PIN       -1
-
-#define Z_STEP_PIN         62
-#define Z_DIR_PIN          63
-#define Z_ENABLE_PIN       -1
-
-#define E0_STEP_PIN        65
-#define E0_DIR_PIN         66
-#define E0_ENABLE_PIN      -1
-
-//
-// Temperature Sensors
-//
-#define TEMP_0_PIN          6   // Analog Input
-#define TEMP_BED_PIN       10   // Analog Input
-
-//
-// Heaters / Fans
-//
-#define HEATER_0_PIN       13
-#define HEATER_BED_PIN      4
-
-//
-// Misc. Functions
-//
-#define SDSS               53
-#define PS_ON_PIN           9