Fixed building on Mac OS X on the command line and with an older macOS SDK

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rename : src/joystick/darwin/SDL_sysjoystick.c => src/joystick/darwin/SDL_iokitjoystick.c
rename : src/joystick/darwin/SDL_sysjoystick_c.h => src/joystick/darwin/SDL_iokitjoystick_c.h
rename : src/joystick/iphoneos/SDL_sysjoystick.m => src/joystick/iphoneos/SDL_mfijoystick.m
rename : src/joystick/iphoneos/SDL_sysjoystick_c.h => src/joystick/iphoneos/SDL_mfijoystick_c.h
9 files changed