C++: Modernize the files tests.

Author: geoffw0

cpp/ql/test/library-tests/files/FilePath.expected

@@ -0,0 +1,4 @@
+| c.c | library-tests/files/c.c | CFile, MetricFile | C |  |  |
+| files1.cpp | library-tests/files/files1.cpp | CppFile, MetricFile | C++ | swap | t |
+| files1.h | library-tests/files/files1.h | HeaderFile, MetricFile |  | swap |  |
+| files2.cpp | library-tests/files/files2.cpp | CppFile, MetricFile | C++ | g | x, y |

cpp/ql/test/library-tests/files/FilePath.ql

@@ -0,0 +1,15 @@
+import cpp
+
+string describe(File f) {
+  f.compiledAsC() and
+  result = "C"
+  or
+  f.compiledAsCpp() and
+  result = "C++"
+}
+
+from File f
+where f.toString() != ""
+select f.toString(), f.getRelativePath(), concat(f.getAQlClass().toString(), ", "),
+  concat(describe(f), ", "), concat(f.getATopLevelDeclaration().toString(), ", "),
+  concat(LocalVariable v | f.getADeclaration() = v | v.toString(), ", ")