C++: Add support for getting literals in using declarations #607

Job	Run time
Model Difference (apache/commons-codec)	3m 18s
Model Difference (apache/commons-fileupload)	3m 13s
Model Difference (apache/dubbo)	3m 14s
Model Difference (apache/commons-lang)	3m 28s
Model Difference (apache/commons-csv)	3m 3s
Model Difference (apache/commons-validator)	3m 14s
Model Difference (apache/commons-io)	3m 21s
Model Difference (apache/commons-logging)	2m 59s
Model Difference (apache/commons-beanutils)	3m 18s
	29m 8s

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