Summary: several diagnostic improvements
Reviewed-by: jjg

Reviewed-by: mcimadamore

Summary: synthetic name clash check should not apply to miranda methods
Reviewed-by: jjg
Contributed-by: tomas.zezula@sun.com

Reviewed-by: darcy

Summary: Race condition between symbol completion and attribution of import statements causes NPE when creating intersection type
Reviewed-by: jjg

6920317: package-info.java file has to be specified on the javac cmdline, else it will not be avail.
Reviewed-by: darcy