Don't compile delay hook into libsass

Windows delay hook feature is only needed
on the main module, linked into the shared
library. Don't compile and include
it second time in the bundled libsass.

Related: https://github.com/nodejs/node-gyp/issues/732

src/libsass.gyp

@@ -2,6 +2,7 @@
   'targets': [
     {
       'target_name': 'libsass',
+      'win_delay_load_hook': 'false',
       'type': 'static_library',
       'defines': [
          'LIBSASS_VERSION="<!(node -e "process.stdout.write(require(\'../package.json\').libsass)")"'