Argument newlines between arguments removal

The macro name and the first argument, and any two consecutive arguments, can be optionally separated by exactly one newline character, e.g.:is equivalent to:which is also equivalent to:This allows to greatly improve the readability of long argument lists by having them one per line.

There is one exception to this however: inside an insane header, any newline is interpreted as the end of the insane header. This is why the following works as expected:and the id gets assigned to the header rather than the trailing code element.