C++: Add test for $` escaping

Author: jketema

cpp/ql/test/query-tests/Diagnostics/ExtractionErrors.expected

@@ -1,2 +1,3 @@
+| containserror.cpp:9:14:9:14 | Recoverable extraction error: 'x' has already been declared in the current scope | Extraction failed in containserror.cpp with error "containserror.cpp", line 9: error: "x" has already been declared in the current scope\n  \tconst char *x = "Foo2 $$@ bar2 $$@ baz2";\n  \t            ^\n\n | 2 |
 | doesnotcompile.cpp:4:2:4:2 | Recoverable extraction error: identifier 'This' is undefined | Extraction failed in doesnotcompile.cpp with error "doesnotcompile.cpp", line 4: error: identifier "This" is undefined\n  \tThis is not correct C/C++ code.\n  \t^\n\n | 2 |
 | doesnotcompile.cpp:4:10:4:10 | Recoverable extraction error: expected a ';' | Extraction failed in doesnotcompile.cpp with error "doesnotcompile.cpp", line 4: error: expected a ";"\n  \tThis is not correct C/C++ code.\n  \t        ^\n\n | 2 |

cpp/ql/test/query-tests/Diagnostics/ExtractionWarnings.expected

@@ -1,2 +1,3 @@
+| containserror.cpp:9:14:9:14 | Recoverable extraction error: 'x' has already been declared in the current scope | Extraction failed in containserror.cpp with warning "containserror.cpp", line 9: error: "x" has already been declared in the current scope\n  \tconst char *x = "Foo2 $$@ bar2 $$@ baz2";\n  \t            ^\n\n | 1 |
 | doesnotcompile.cpp:4:2:4:2 | Recoverable extraction error: identifier 'This' is undefined | Extraction failed in doesnotcompile.cpp with warning "doesnotcompile.cpp", line 4: error: identifier "This" is undefined\n  \tThis is not correct C/C++ code.\n  \t^\n\n | 1 |
 | doesnotcompile.cpp:4:10:4:10 | Recoverable extraction error: expected a ';' | Extraction failed in doesnotcompile.cpp with warning "doesnotcompile.cpp", line 4: error: expected a ";"\n  \tThis is not correct C/C++ code.\n  \t        ^\n\n | 1 |

cpp/ql/test/query-tests/Diagnostics/Info.expected

@@ -1,4 +1,4 @@
-| containserror.cpp:0:0:0:0 | containserror.cpp | containserror.cpp | fromSource, normalTermination |
+| containserror.cpp:0:0:0:0 | containserror.cpp | containserror.cpp | ExtractionProblem (severity 1), fromSource, normalTermination |
 | containswarning.cpp:0:0:0:0 | containswarning.cpp | containswarning.cpp | fromSource, normalTermination |
 | doesnotcompile.cpp:0:0:0:0 | doesnotcompile.cpp | doesnotcompile.cpp | ExtractionProblem (severity 1), fromSource, normalTermination |
 | file://:0:0:0:0 |  |  |  |

cpp/ql/test/query-tests/Diagnostics/containserror.cpp

@@ -3,3 +3,8 @@
 void containserror() {
 	#error An error!
 }
+
+void error_with_placeholder() {
+	const char *x = "Foo1 $@ bar1 $@ baz1";
+	const char *x = "Foo2 $@ bar2 $@ baz2";
+}