Fix escape sequences in test cases (#3499)

Author: chrchr-github

test/teststl.cpp

@@ -534,8 +534,8 @@ class TestStl : public TestFixture {
                     "  if (DirName == nullptr)\n"
                     "      return {};\n"
                     "  std::string Name{ DirName };\n"
-                    "  if (!Name.empty() && Name.back() != '\\')\n"
-                    "    Name += '\\';\n"
+                    "  if (!Name.empty() && Name.back() != '\\\\')\n"
+                    "    Name += '\\\\';\n"
                     "  return Name;\n"
                     "}\n");
         ASSERT_EQUALS("", errout.str());

test/testvalueflow.cpp

@@ -6047,8 +6047,8 @@ class TestValueFlow : public TestFixture {
                "            && ch != '(' && ch != ')'\n"
                "            && ch != '[' && ch != ']'\n"
                "            && ch != ';' && ch != ','\n"
-               "            && ch != '#' && ch != '\\'\n"
-               "            && ch != '\'' && ch != '\"');\n"
+               "            && ch != '#' && ch != '\\\\'\n"
+               "            && ch != '\\\'' && ch != '\\\"');\n"
                "}\n";
         valueOfTok(code, "return");
     }