[nacltoons] Move nacl-specific build to proj.nacl

Also, move win32 specific code to proj.win32.

R=binji@chromium.org

Review URL: https://codereview.chromium.org/14851014

git-svn-id: https://nativeclient-sdk.googlecode.com/svn/trunk/src@1547 050acbb0-2703-11df-ab0a-9f3f633ae91d