Now the query 'concl >= _ | ".*vsum.*"' terminates on the medium-sized HOL
light extraction

a query like 'concl = _' was returning justifications of the form

_ found in hypothesis

Now only really relevant justifications are returned

Signed-off-by: Claudio Sacerdoti Coen <claudio.sacerdoticoen@unibo.it>

1. during indexing using --source=PATH one can add indexing information
   mapping LP identifiers to Coq identifiers and locations
2. when the search results are shown, the Coq code is also printed if
   the LP identifier is found in the map in point 1

The code to generate the file used in 1 should belong to HOL2DK. Right now
we have hacked some best-effort shell script that we will commit in the
HOL2DK_indexing repository

It used to match only prefixes of strings, which was quite weird

Note: there's no easy way to implement the same check for rules.
However it is unlikely to index twice a file that contains only
rewriting rules.

E.g. in last rewriting rule in tests/OK/coercions.lp

1. we used a Timed.ref to update the indexes with the local development
 (i.e. just the files that have been required, not the others) so that it
 is possible to query the local development
2. when doing "require ... as Foo" the user can use Foo.X in the queries;
 (but not regular expressions involving Foo, but that seems reasonable)

We have introduced some "hakish" code here and there to be reviewed. In
particular:

1. we store in Common/Mode if we are running LSP
2. we detected that the current LSP buffer has "fname" set to an URI
   "file:///". We use this feature to distinguish between the buffer
   and the filesystem so that, when showing query results to the user,
   if the text comes from the buffer we can retrieve it
3. we use a finely tuned combination of Stdlib.ref/Timed.ref to "remember"
   things that would be forgotten. E.g.:
   a) we remember the LSP buffer content *after* the end of the compilation
   b) we remember the index *after* the end of the indexing of a single
      file
4. we used a maison stream-like representation of file contents to be able
   to retrieve the text to be shown to the user both from the filesystem
   or from strings (i.e. the content of the LSP buffer)
5. since indexing is now performed even during compilation when things
   enter a signature in LSP mode, we created a huge circular dependency
   in the modules that we break using multiple callbacks and Stdlib.ref
   that are set here and there. Maybe one can do (much) better.
   In particular pure now depends on tool.

- doc and welcome page of websearch to be updated with the new syntax
- in "lambdapi search" and VScode -> and forall cannot be used any more
- the new syntax allows all the LP syntax plus:
  t ::= ... | forall binders, t | exists binders, t | fun binders => t
            | t -> t
- the binders used in the new entries allow also "x ... z : t" that is
  currently rejected by LP (but it is allowed in Coq)

TODO: but for exists, all the Coq's stdlib notations are NOT in place
(e.g. arithmetic/logic connectives, numbers, ...). How should we add them?
Maybe one possible path is to have "special" notation files that can be fed
to websearch when it starts. As for rewriting rules for normalization, the
notation files are supposed to add notation to symbols that have NOT been
put in the environment. It may be feasible: the file that calls Pratter
already uses our find_sym to resolve symbols!

- this basically removes ALL overloaded problems from the HOL export
- the code is written so that the two normalized symbols may be
  unequal (in the sense of =) but have the same path. Maybe one should
  investigate why this is necessary, but for the time being it is safe
  to ignore. [ We are probably comparing a real symbol with a bogus one
  or even two bogus ones that differ ]

…kept

Example: Real was no longer found because it must become R and not Real

In particular one can require (and open) theory_hol.lp and then
require (and open) a notation.lp file to add infix notation.

…ase rewrite the query replacing...