[ASTImporter] Add test for SwitchStmt

[a_sidorin]

Thank you for working on this!

cfe/trunk/test/Import/switch-stmt/Inputs/F.cpp

+void f() {
+  switch (1) {
+  case 1:
+  case 2:
+    break;
+  }
+  switch (int varname; 1) {
+  case 1:
+    break;
+  case 2:
+    break;
+  }
+  switch (1)
+  default:
+    break;
+  switch (0)
+    ;
+}

cfe/trunk/test/Import/switch-stmt/test.cpp

+// RUN: clang-import-test -dump-ast -import %S/Inputs/F.cpp -expression %s | FileCheck %s
+
+// CHECK: SwitchStmt
+// CHECK-NEXT: <<NULL>>
+// CHECK-NEXT: <<NULL>>
+// CHECK-NEXT: IntegerLiteral
+// CHECK-NEXT: CompoundStmt
+// CHECK-NEXT: CaseStmt
+// CHECK-NEXT: IntegerLiteral
+// CHECK-NEXT: <<NULL>>
+// CHECK-NEXT: CaseStmt
+// CHECK-NEXT: IntegerLiteral
+// CHECK-NEXT: <<NULL>>
+// CHECK-NEXT: BreakStmt
+
+// CHECK: SwitchStmt
+// CHECK-NEXT: DeclStmt
+// CHECK-NEXT: VarDecl
+// CHECK-SAME: varname
+// CHECK-NEXT: <<NULL>>
+// CHECK-NEXT: IntegerLiteral
+// CHECK-NEXT: CompoundStmt
+// CHECK-NEXT: CaseStmt
+// CHECK-NEXT: IntegerLiteral
+// CHECK-NEXT: <<NULL>>
+// CHECK-NEXT: BreakStmt
+// CHECK-NEXT: CaseStmt
+// CHECK-NEXT: IntegerLiteral
+// CHECK-NEXT: <<NULL>>
+// CHECK-NEXT: BreakStmt
+
+// CHECK: SwitchStmt
+// CHECK-NEXT: <<NULL>>
+// CHECK-NEXT: <<NULL>>
+// CHECK-NEXT: IntegerLiteral
+// CHECK-NEXT: DefaultStmt
+// CHECK-NEXT: BreakStmt
+
+// CHECK: SwitchStmt
+// CHECK-NEXT: <<NULL>>
+// CHECK-NEXT: <<NULL>>
+// CHECK-NEXT: IntegerLiteral
+// CHECK-NEXT: NullStmt
+
+void expr() {
+  f();
+}