C has two namespaces and the database had one. A typedef of a tag's
name wiped it.
Tags, i.e. struct, enum and union, share one namespace; they move to a
table of their own. A name resolves the way C does: the ordinary
identifier first, the tag when that leads nowhere.
While resolving a typedef, the target was taken apart with cadr
whatever it was, so (typedef points (¤ point 4)) reported point's
fields as its own -- an array of four points claiming to be a point,
and a macro reaching through it with v->x. Only a name and
(struct|union|enum NAME) name a type now.
Introducing Sex SEMantic ENgine: the semen.
Also split reader to other file (it can be replaced in the future).
Macro expansion inside Sex code doesn't work yet, and it must be done
in semen, not during fmt-c generation as before.
