How to write doxygen documentation for macro.

There are two typical types of macro definitions.

• One is to define constant macros. For this type of macro, we recommend putting documentation after members. See DOXYGEN_EXAMPLE_CONST_A and DOXYGEN_EXAMPLE_CONST_B in documentation/0.doxygen/example/include/macro.h for exmaple.
• The other is to define macros with parameters. For this type of macro, we recommend using a method similar to documenting for functions, that is, writing comment block before the macro definition. More details please see How to write doxygen documentation for function. See DOXYGEN_EXAMPLE_ABS in documentation/0.doxygen/example/include/macro.h for example.