[gwt-contrib] Updating apichecker for GWT 2.4. (issue1447807)

[jlabanca]

Reviewers: rjrjr,

Description:
Updating apichecker for GWT 2.4.

Please review this at http://gwt-code-reviews.appspot.com/1447807/

Affected files:
  M build.xml
  A tools/api-checker/config/gwt23_24userApi.conf
  M tools/api-checker/reference/README
  M tools/api-checker/reference/createApiCheckerReferenceJars.sh
  M  
tools/api-checker/src/com/google/gwt/tools/apichecker/ApiCompatibilityChecker.java


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