Added new ASTWalker behavior

examples/factRec.dusk

examples/factor.dusk

examples/fibonacci.dusk

examples/funcDecl.dusk

examples/gcd.dusk

examples/inOut.dusk

examples/interpRec.dusk

examples/isPrime.dusk

include/dusk/AST/ASTVisitor.h

include/dusk/AST/ASTWalker.h

include/dusk/AST/Decl.h

include/dusk/AST/Expr.h

include/dusk/AST/Pattern.h

include/dusk/AST/Stmt.h

include/dusk/AST/TypeRepr.h

lib/AST/ASTNode.cpp

lib/AST/ASTPrinter.cpp

lib/AST/ASTWalker.cpp

lib/IRGen/CMakeLists.txt

lib/IRGen/GenExpr.cpp