- Add QIRIf in visitors

src/qir/ast/data/QIRTable.java

src/qir/ast/value/QIRBaseValue.java

src/qir/ast/value/QIRString.java

src/qir/driver/PostgreSQLDriver.java

src/qir/driver/QIRSQLVisitor.java

src/qir/reduction/QIRGreedyReduceVisitor.java

src/qir/util/IQIRVisitor.java

src/qir/util/QIRFreeVarsVisitor.java