Add option to change preprocessor -CC to -C

See #37.

include/cppast/libclang_parser.hpp

@@ -27,6 +27,8 @@ namespace cppast
             static bool write_preprocessed(const libclang_compile_config& config);
 
             static bool fast_preprocessing(const libclang_compile_config& config);
+
+            static bool remove_comments_in_macro(const libclang_compile_config& config);
         };
 
         void for_each_file(const libclang_compilation_database& database, void* user_data,
@@ -144,6 +146,15 @@ namespace cppast
             fast_preprocessing_ = b;
         }
 
+        /// \effects Sets whether or not documentation comments generated by macros are removed.
+        /// Default value is `false`.
+        /// \notes If this leads to an error due to preprocessing and comments, you have to enable it.
+        /// \notes If this is `true`, `clang` will be invoked with `-CC`, otherwise `-C`.
+        void remove_comments_in_macro(bool b) noexcept
+        {
+            remove_comments_in_macro_ = b;
+        }
+
     private:
         void do_set_flags(cpp_standard standard, compile_flags flags) override;
 
@@ -162,6 +173,7 @@ namespace cppast
         int         clang_version_;
         bool        write_preprocessed_ : 1;
         bool        fast_preprocessing_ : 1;
+        bool        remove_comments_in_macro_ : 1;
 
         friend detail::libclang_compile_config_access;
     };