Give a class to the types MEOS registers in no enum

[estebanzimanyi]

PCSCHEMA, RTree, SPTree and MeosArray are MEOS's own — declared in the
umbrella headers, api=public, with their whole operation set published — and
the model gives them no class, so every method naming one is untypable. The
point-cloud accessors are where that bites: pcpoint_get_x, _get_y, _get_z,
_get_dim and pcpoint_to_tpcbox each take the schema the value is read
through, and a binding with no class for it reaches none of them.

They sit in Value beside the base values rather than in a hierarchy of their
own. To a binding a pointer to a struct is one thing — an instance it holds and
calls through — whether MEOS publishes the struct's layout or forward-declares
it, and GoMEOS's wrapper table draws no line between the two either: SkipList,
RTree, PJ_CONTEXT and gsl_rng are wrapped exactly as Temporal and Set
are. What they do state is a null temptype, MEOS registering them in no enum,
written out rather than left out so an unregistered type cannot read as one
nobody got round to. 67 functions reach a class this way, and none moves off the
class it had.

A class nothing is CALLED on takes the type it MAKES. Nothing is called on a
schema — every accessor takes one as an argument — so the receiver says nothing
and meos_pc_schema answering a PCSCHEMA * is what does. The char * answers
beside it say nothing, a string being no class's instance.

meos_pc_schema IS its class's prefix, so dropping the prefix leaves no member
name at all. That is the one case the override table exists for, and it now says
so; the schema cache's lookup reads get.