[basic.compound] Weird and conflicting uses of `defnx`

[eisenwave]

draft/source/basic.tex

Lines 5950 to 5957 in c7015b4

	\item
	\defnx{classes}{class} containing a sequence of class members\iref{class,class.mem},
	and a set of restrictions
	on the access to these entities\iref{class.access};
	\item
	\defnx{unions}{\idxcode{union}}, which are classes capable of containing objects of
	different types at different times, \ref{class.union};

There is no logic to these uses of defnx in https://eel.is/c++draft/basic.compound.

This intro fluff paragraph is really just a note that summarizes the various forms of forming compound types; it doesn't define anything and so all the uses of defnx should probably be removed here.

What's even more problematic is that it breaks the spec by having multiple definitions of the same term, such as

• https://eel.is/c++draft/class.union.general#def:union defining "union"
• https://eel.is/c++draft/basic.compound#def:union defining union (which seems defective in itself because how is a prose paragraph "defining" a keyword? The grammar does that.)