ith empty macro bodies.
<br>Some symbols of the same meaning come in various forms. Only one of
such symbols should be specified explicitly, all others should be equated
to that primary definition. According to newer C specs the names with 2
leading underscores are the primary symbols. All variations should be defined,
to definitely prevent unrecognized identifiers.
<p>The value (parser) applies to extensions which should be ignored if
not handled by the parser. The primary symbol is defined as empty