Backend: Enumerations don't produce correct start value in init file

[Martin Sjölund]

{{{class A
type E = enumeration(a,b);
E e(start = E.b) = E.a;
end A;}}}

To fix:
DAEUtil.getStartAttrFail needs to be able to return start value for enum
SimCode.printExpStrOpt needs to print the index if the constant is an enum

Easiest to fix after Per commits his other enum fixes

[Pavol Privitzer]

This issue will be solved when init file is generated from templates using SIMVAR.initialValue and addition of:

case (SOME(DAE.VAR_ATTR_ENUMERATION(start = SOME(r)))) then r;

to DAEUtil.getStartAttrFail()

[Martin Sjölund]

OM 1.6.0 has these as part of the init-file