[clang-doc] Add regression test for test comments in macros (llvm#132510)

Fixes llvm#59819. The underlying
problem was fixed in https://reviews.llvm.org/D142560, but this patch
adds a proper regression test.

Author: ZhongUncle

clang-tools-extra/test/clang-doc/comments-in-macros.cpp

@@ -0,0 +1,35 @@
+// Regression test for https://github.com/llvm/llvm-project/issues/59819
+
+// RUN: rm -rf %t && mkdir -p %t
+// RUN: clang-doc --format=md --doxygen --output=%t --executor=standalone %s
+// RUN: FileCheck %s < %t/GlobalNamespace/MyClass.md --check-prefix=MD-MYCLASS-LINE
+// RUN: FileCheck %s < %t/GlobalNamespace/MyClass.md --check-prefix=MD-MYCLASS
+
+// RUN: clang-doc --format=html --doxygen --output=%t --executor=standalone %s
+// RUN: FileCheck %s < %t/GlobalNamespace/MyClass.html --check-prefix=HTML-MYCLASS-LINE
+// RUN: FileCheck %s < %t/GlobalNamespace/MyClass.html --check-prefix=HTML-MYCLASS
+
+#define DECLARE_METHODS                                           \
+    /**   							  
+     * @brief Declare a method to calculate the sum of two numbers
+     */                                                           \
+    int Add(int a, int b) {                                       \
+        return a + b;                                             \
+    }
+
+// MD-MYCLASS: ### Add
+// MD-MYCLASS: *public int Add(int a, int b)*
+// MD-MYCLASS: **brief** Declare a method to calculate the sum of two numbers
+
+// HTML-MYCLASS: <p>public int Add(int a, int b)</p>
+// HTML-MYCLASS: <div>brief</div>
+// HTML-MYCLASS: <p> Declare a method to calculate the sum of two numbers</p>
+
+
+class MyClass {
+public:
+// MD-MYCLASS-LINE: *Defined at {{.*}}clang-tools-extra{{[\/]}}test{{[\/]}}clang-doc{{[\/]}}comments-in-macros.cpp#[[@LINE+2]]*
+// HTML-MYCLASS-LINE: <p>Defined at line [[@LINE+1]] of file {{.*}}clang-tools-extra{{[\/]}}test{{[\/]}}clang-doc{{[\/]}}comments-in-macros.cpp</p>
+    DECLARE_METHODS
+};
+