[clang] [clang-tools-extra] Associate documentation comments with macro definitions (PR #198452)

[Egor Zhdan via cfe-commits]

================
@@ -0,0 +1,27 @@
+// Run lines are sensitive to line numbers and come below the code.
+
+/// Greeting count.
+#define HELLO 1
+
+#define BARE 2
+
+/**
+ * \brief Add two numbers.
+ */
+#define SUM(x, y) ((x) + (y))
+
+#define TRAILING 3 ///< Trailing macro doc.
+
----------------
egorzhdan wrote:

Is it worth having a test with a redefined macro? e.g.
```cpp
/// abc
#define REDEFINED 123

/// def
#define REDEFINED 456
```

https://github.com/llvm/llvm-project/pull/198452