Fixes a problem where samples that include a generator fail to build, because the sample's bin directory is not on the classpath.  The gwtc rule now includes a sample's bin directory.

Patch by: bobv
Review by: me


git-svn-id: https://google-web-toolkit.googlecode.com/svn/trunk@1231 8db76d5a-ed1c-0410-87a9-c151d255dfc7