Merge specifications into program types, as JCF intended.

number and names of hypotheses.

The hypotheses that are conjunctions or exists are also named accordingly

The API guarantees that a given psymbol cannot be defined in
two different ways and thus cannot have two different specs.

Thus, we do not need to look through two different namespaces.
The only difference w.r.t. the core namespace semantics is that
a program symbol (pvsymbol, psymbol, plsymbol, or xsymbol) may
be introduced in the scope of an lsymbol of the same name and
overshadow it in program expressions, though not in specifications.
For example, the following declarations allow to use (!) both in
programs and specifications:

    type ref 'a = {| mutable contents : 'a |}
    function (!) (x: ref 'a) : 'a = x.contents
    let (!) (r: ref 'a) = {} r.contents { result = !r }

Notice, however, that itsymbols cannot overshadow pure tsymbols.