glsl: Keep track of the early_fragment_tests flag in gl_shader.

And rename _mesa_glsl_parse_state::early_fragment_tests to
fs_early_fragment_tests for consistency with other FS-specific flags in the
same struct.

Reviewed-by: Matt Turner <mattst88@gmail.com>
diff --git a/src/glsl/linker.cpp b/src/glsl/linker.cpp
index 21fde94..330fae0 100644
--- a/src/glsl/linker.cpp
+++ b/src/glsl/linker.cpp
@@ -1413,6 +1413,8 @@
          linked_shader->origin_upper_left = shader->origin_upper_left;
          linked_shader->pixel_center_integer = shader->pixel_center_integer;
       }
+
+      linked_shader->EarlyFragmentTests |= shader->EarlyFragmentTests;
    }
 }