nicer formatting of IScriptType when the value of a IVariable is a
IScriptValue (nested toString)
fix for:
java.lang.NullPointerException
at
org.eclipse.dltk.internal.javascript.validation.TypeInfoValidator$ValidationVisitor.describeArguments(TypeInfoValidator.java:1524)
at
org.eclipse.dltk.internal.javascript.validation.TypeInfoValidator$ValidationVisitor.validateCallExpressionRMethod(TypeInfoValidator.java:1205)
at
org.eclipse.dltk.internal.javascript.validation.TypeInfoValidator$ValidationVisitor.validateCallExpression(TypeInfoValidator.java:1047)

because getDeclaredType was not stable it could return constantly a
different value. Now it is more stable because the value that has a
declared value is always preferred over a value that just has types