void addEnumGroup(EnumGroup enumGroup)
    {
        if (enumGroups.put(enumGroup.name, enumGroup) != null)
            throw err("Duplicate enum: " + enumGroup.name, this);
    }
Returns the java package name that was configured in the proto. Note that {@link #getJavaPackageName()} will have
the same value as this, if the compiler options did not have entries that override it.
protostuff-parser/src/main/java/io/protostuff/parser/Proto.java