Type reification code does not support character class combinators such as || union

[jurgenvinju]

Describe the bug

The interpreter crashes on #[a-z] || [A-Z] with an ambiguity:

rascal>#[a-z] || [A-Z]
Unexpected failure during parsing of current command: 
Ambiguous code (internal error), #[a-z] || [A-Z]
org.rascalmpl.interpreter.asserts.Ambiguous: Ambiguous code (internal error), #[a-z] || [A-Z]
        at org.rascalmpl.parser.uptr.UPTRNodeFactory.buildAmbiguityNode(UPTRNodeFactory.java:76)
        at org.rascalmpl.parser.uptr.UPTRNodeFactory.createAmbiguityNode(UPTRNodeFactory.java:85)
        at org.rascalmpl.parser.uptr.UPTRNodeFactory.createAmbiguityNode(UPTRNodeFactory.java:1)
        at org.rascalmpl.parser.gtd.result.out.SortContainerNodeFlattener.convertToUPTR(SortContainerNodeFlattener.java:183)
        at org.rascalmpl.parser.gtd.result.out.DefaultNodeFlattener.convert(DefaultNodeFlattener.java:63)

brackets don't help:

rascal>#([a-z] || [A-Z])
Unexpected failure during parsing of current command: 
Ambiguous code (internal error), ([a-z] || [A-Z])
org.rascalmpl.interpreter.asserts.Ambiguous: Ambiguous code (internal error), ([a-z] || [A-Z])
        at org.rascalmpl.parser.uptr.UPTRNodeFactory.buildAmbiguityNode(UPTRNodeFactory.java:76)
        at org.rascalmpl.parser.uptr.UPTRNodeFactory.createAmbiguityNode(UPTRNodeFactory.java:85)
        at org.rascalmpl.parser.uptr.UPTRNodeFactory.createAmbiguityNode(UPTRNodeFactory.java:1)