Remove octal escape literals from the codebase

Octal escape literals are deprecated and will be removed in the
next Scala version.
Merge pull request #2988 from sschaef/remove-octal-literals

Remove octal escape literals from the codebase
SI-6762 rename emptyValDef to noSelfType.

Looks like emptyValDef.isEmpty was already changed to return
false, so now all that's left is a name which means something.