Fix issue where original ATN would be damaged by IntervalSet operations. Foxes #3216
Fix issue where original ATN would be damaged by IntervalSet operations. Foxes #3216

ericvergnaud/antlr4,antlr/antlr4,ericvergnaud/antlr4,antlr/antlr4,ericvergnaud/antlr4,antlr/antlr4,parrt/antlr4,ericvergnaud/antlr4,parrt/antlr4,ericvergnaud/antlr4,antlr/antlr4,parrt/antlr4,parrt/antlr4,antlr/antlr4,ericvergnaud/antlr4,parrt/antlr4,parrt/antlr4,antlr/antlr4,ericvergnaud/antlr4,parrt/antlr4,ericvergnaud/antlr4,ericvergnaud/antlr4,parrt/antlr4,parrt/antlr4,antlr/antlr4,antlr/antlr4,parrt/antlr4,antlr/antlr4,antlr/antlr4,ericvergnaud/antlr4