Add copyright headers to remaining gyp files.

gyp/core.gyp

+# Copyright 2015 Google Inc.
+#
+# Use of this source code is governed by a BSD-style license that can be
+# found in the LICENSE file.
 # Core Skia library code.
 {
   'targets': [
     {
       'target_name': 'core',
       'product_name': 'skia_core',
       'type': 'static_library',
       'standalone_static_library': 1,
       'msvs_guid': 'B7760B5E-BFA8-486B-ACFD-49E3A6DE8E76',
 
@@ skipping 108 matching lines @@
           [ 'skia_os == "win"', {
             'include_dirs': [
               'config/win',
             ],
           }],
         ],
       },
     },
   ],
 }