Adds part of Java 7 new language features.

Adds the Java 7 new language features: namely, the diamond operator, new numerical
literal formats, and switch/case on string literals.

Adds a new flag -source to select source level compatibility (java 6 or java 7);
-source defaults to java 6.

Fixes issue 6633.

Change-Id: I91c1f39ff20a2e7ac131d647bf4c96e34ce47a70
Review-Link: https://gwt-review.googlesource.com/#/c/2650/
36 files changed