shader: Enable tesselation extension manually for GLSL version < 3.20

GLES 3.1 might support tesselation shaders through the extension, but
this requires the extension to be enabled manually.

Signed-off-by: Gert Wollny <gert.wollny@collabora.com>
Reviewed-by: Dave Airlie <airlied@redhat.com>

src/vrend_shader.c

@@ -3995,6 +3995,13 @@ static char *emit_header(struct dump_ctx *ctx, char *glsl_hdr)
          STRCAT_WITH_RET(glsl_hdr, "#extension GL_OES_texture_storage_multisample_2d_array : require\n");
       if (ctx->prog_type == TGSI_PROCESSOR_GEOMETRY)
          STRCAT_WITH_RET(glsl_hdr, "#extension GL_EXT_geometry_shader : require\n");
+
+      if ((ctx->prog_type == TGSI_PROCESSOR_TESS_CTRL ||
+           ctx->prog_type == TGSI_PROCESSOR_TESS_EVAL)) {
+         if (ctx->cfg->glsl_version < 320)
+            STRCAT_WITH_RET(glsl_hdr, "#extension GL_OES_tessellation_shader : require\n");
+      }
+
       PAD_GPU_SHADER5(glsl_hdr);
       STRCAT_WITH_RET(glsl_hdr, "precision highp float;\n");
       STRCAT_WITH_RET(glsl_hdr, "precision highp int;\n");