And also redefined built-ins that are not used.

From Section 7.4.1 (Shader Interface Matching) of the OpenGL 4.60
spec:

  " To use any built-in input or output in the gl_PerVertex block in
    separable program objects, shader code must redeclare that block
    prior to use. A separable program will fail to link if:

      * it contains multiple shaders of a single type with different
         redeclarations of this built-in block; or

      * any shader uses a built-in block member not found in the
        redeclaration of that block.

    There is one exception to this rule described below.

    As described above, an exact interface match requires matching
    built-in input and output blocks. At an interface between two
    non-fragment shader stages, the gl_PerVertex input and output
    blocks are considered to match if and only if the block members
    match exactly in name, type, qualification, and declaration order.
    At an interface involving the fragment shader stage, the presence
    or absence of any built-in output does not affect interface
    matching."

Signed-off-by: Andres Gomez <agomez@igalia.com>
Reviewed-by: Tapani Pälli <tapani.palli@intel.com>
Reviewed-by: Martin Peres <martin.peres@linux.intel.com>