Fixes a compiler error by using null joystick on freebsd

[jamesmintram]

Created a separate c file for freebsd and updated the joystick ref to use the null joystick.

Built, compiled and ran OpenDiablo which is where this issue was discovered. #264 (comment)

@pwaller

[nunotexbsd]

Hello,

I used latest upstream and it seams its not solved:

"s' in 'struct _GLFWjoystick'
../../go/pkg/mod/github.com/go-gl/glfw/v3.3/[email protected]/glfw/src/linux_joystick.c:89:49: error: no member named 'linjs' in 'struct _GLFWjoystick'
../../go/pkg/mod/github.com/go-gl/glfw/v3.3/[email protected]/glfw/src/linux_joystick.c:92:31: error: incomplete definition of type 'struct input_absinfo'
../../go/pkg/mod/github.com/go-gl/glfw/v3.3/[email protected]/glfw/src/linux_joystick.c:89:22: note: forward declaration of 'struct input_absinfo'
../../go/pkg/mod/github.com/go-gl/glfw/v3.3/[email protected]/glfw/src/linux_joystick.c:92:47: error: incomplete definition of type 'struct input_absinfo'
../../go/pkg/mod/github.com/go-gl/glfw/v3.3/[email protected]/glfw/src/linux_joystick.c:89:22: note: forward declaration of 'struct input_absinfo'
../../go/pkg/mod/github.com/go-gl/glfw/v3.3/[email protected]/glfw/src/linux_joystick.c:96:44: error: incomplete definition of type 'struct input_absinfo'
../../go/pkg/mod/github.com/go-gl/glfw/v3.3/[email protected]/glfw/src/linux_joystick.c:89:22: note: forward declaration of 'struct input_absinfo'
../../go/pkg/mod/github.com/go-gl/glfw/v3.3/[email protected]/glfw/src/linux_joystick.c:109:32: error: use of undeclared identifier 'ABS_CNT'
../../go/pkg/mod/github.com/go-gl/glfw/v3.3/[email protected]/glfw/src/linux_joystick.c:111:17: error: no member named 'linjs' in 'struct _GLFWjoystick'
../../go/pkg/mod/github.com/go-gl/glfw/v3.3/[email protected]/glfw/src/linux_joystick.c:114:43: error: no member named 'linjs' in 'struct _GLFWjoystick'
../../go/pkg/mod/github.com/go-gl/glfw/v3.3/[email protected]/glfw/src/linux_joystick.c:116:13: warning: implicit declaration of function 'ioctl' is invalid in C99 [-Wimplicit-function-declaration]
../../go/pkg/mod/github.com/go-gl/glfw/v3.3/[email protected]/glfw/src/linux_joystick.c:116:23: error: no member named 'linjs' in 'struct _GLFWjoystick'
../../go/pkg/mod/github.com/go-gl/glfw/v3.3/[email protected]/glfw/src/linux_joystick.c:116:33: warning: implicit declaration of function 'EVIOCGABS' is invalid in C99 [-Wimplicit-function-declaration]
../../go/pkg/mod/github.com/go-gl/glfw/v3.3/[email protected]/glfw/src/linux_joystick.c:119:38: error: incomplete definition of type 'struct input_absinfo'
../../go/pkg/mod/github.com/go-gl/glfw/v3.3/[email protected]/glfw/src/linux_joystick.c:114:16: note: forward declaration of 'struct input_absinfo'
../../go/pkg/mod/github.com/go-gl/glfw/v3.3/[email protected]/glfw/src/linux_joystick.c:133:41: error: no member named 'linjs' in 'struct _GLFWjoystick'
../../go/pkg/mod/github.com/go-gl/glfw/v3.3/[email protected]/glfw/src/linux_joystick.c:137:23: error: expected ';' after expression
fatal error: too many errors emitted, stopping now [-ferror-limit=]

Thanks,

Nuno