Fixes various mail issues, primarily on IE:
- Mail.html: Adds doctype.
- Contacts: Fixes weird layout issue on IE7 (lots of extra padding).
- Fixes missing space between "Sign Out" and "About".
- Accounts for non-integral unit ratios in layout.
- Fixes inability to drag splitters on IE7.

Review: http://gwt-code-reviews.appspot.com/76803

git-svn-id: https://google-web-toolkit.googlecode.com/svn/trunk@6306 8db76d5a-ed1c-0410-87a9-c151d255dfc7