- adds StringBuilder to the Java emulation classes,
  using the existing implementation from StringBuffer
- makes the emulated StringBuffer be simply a wrapper
  around StringBuilder
- adds some methods to StringBuffer and StringBuilder that
  are new to Java 1.5

Review by: scottb (postmortem)




git-svn-id: https://google-web-toolkit.googlecode.com/svn/trunk@2074 8db76d5a-ed1c-0410-87a9-c151d255dfc7