C++: Don't use PrintAST in a test

Author: calumgrant

cpp/ql/test/library-tests/extraction_errors/ErrorExprs.expected

@@ -0,0 +1,7 @@
+| test.cpp:6:13:6:31 | initializer for x | test.cpp:6:13:6:31 | <error expr> |
+| test.cpp:7:5:7:8 | ExprStmt | file://:0:0:0:0 | <error expr> |
+| test.cpp:8:5:8:23 | ExprStmt | file://:0:0:0:0 | <error expr> |
+| test.cpp:9:5:9:21 | ExprStmt | file://:0:0:0:0 | <error expr> |
+| test.cpp:11:5:11:8 | ExprStmt | file://:0:0:0:0 | <error expr> |
+| test.cpp:15:5:15:8 | ExprStmt | file://:0:0:0:0 | <error expr> |
+| test.cpp:16:5:16:16 | ExprStmt | file://:0:0:0:0 | <error expr> |

cpp/ql/test/library-tests/extraction_errors/ErrorExprs.ql

@@ -0,0 +1,4 @@
+import cpp
+
+from ErrorExpr e
+select e.getParent(), e