GL_ARB_cull_distance extension not supported.

Hi ,
the GL_ARB_cull_distance not be supported for glslang. thanks.

**glslang output :**
```
ERROR: D:\local\Temp\93f5459f-aa34-4345-aec3-1435a5369eb0.tmp:2: '#extension' : extension not supported: GL_ARB_cull_distance
ERROR: D:\local\Temp\93f5459f-aa34-4345-aec3-1435a5369eb0.tmp:2: '#extension' : extra tokens -- expected newline
ERROR: D:\local\Temp\93f5459f-aa34-4345-aec3-1435a5369eb0.tmp:2: '' : compilation terminated
ERROR: 3 compilation errors. No code generated.
```

**shader :**
```
#version 440
#extension GL_ARB_cull_distance : require
#ifndef GL_ARB_cull_distance
#error GL_ARB_cull_distance is undefined
#endif

in float gl_CullDistance[8];

highp float fetch()
{
highp float sum = 0.0;
sum += abs(gl_CullDistance[0]) * 1.0;
sum += abs(gl_CullDistance[1]) * 2.0;
sum += abs(gl_CullDistance[2]) * 3.0;
sum += abs(gl_CullDistance[3]) * 4.0;
sum += abs(gl_CullDistance[4]) * 5.0;
sum += abs(gl_CullDistance[5]) * 6.0;
sum += abs(gl_CullDistance[6]) * 7.0;
sum += abs(gl_CullDistance[7]) * 8.0;
return sum / 72.0;
}

#define ASSIGN_RETURN_VALUE fetch()
out vec4 out_fs;
/* Fragment shader main function */
void main()
{
out_fs = vec4(ASSIGN_RETURN_VALUE, 1.0, 1.0, 1.0);
}
```

No source file or test is named. Start by reproducing the provided shader with glslang and trace how #extension directives and GL_ARB_cull_distance are handled; done means the shader compiles without the reported unsupported-extension errors and the extension macro is defined.

Written by the indexing model from the issue text.