Compatibility mode for projections. c.(p), p c use primitive projs,
while @p refers to an expansion [λ params c, c.(p)]. Recovers almost
entire source compatibility with trunk scripts, except when mixing
@p and p and doing syntactic matching (they're unifiable though).
Add a [Set Primitive Projections] flag to set/unset the use of primitive
projections, selectively for each record. Adapt code to handle both the
legacy encoding and the primitive projections. Library is almost
source-to-source compatible, except for syntactic operations relying
on the presence of parameters. In primitive projections mode, @p refers
to an expansion [λ params r. p.(r)]. More information in CHANGES (to be
reformated/moved to reference manual).