GPR#383: Define _ALL_SOURCE for AIX 7.1

This reverts the parts of commit
9816841 that have been split off into
PRs ocaml#383 and ocaml#386, as well as the Bottom stuff (likely to be unnecessary
as we're considering making `Coercion.compose` a total function).

Print aliases for debug.

Various improvements

* Use `Coercion.t` rather than `Coercion.t option` in many places
* Use `Rec_info.t` again where sensible (in making inlining decisions,
  for instance), but redefine it as `unit` pending the next phase of
  `Rec_info` overhaul
* Add simple `int` fields to `Coercion.t` for changing recursion depth;
  this is simpler than what we'll actually need but specific enough that
  we can test meaningfully (e.g., we can tell whether coercions are
  composed in the right order)

Address a CR

Update .depend

Overhaul Aliases_of_canonical_element; add Alias_set

Also return Bottom from more places (generally anything involved in a
meet).

Use Rec_info.unknown instead of unit

Add comments; simplify `Aliases` API a bit

Revert (most of) "Overhaul Aliases_of_canonical_element; add Alias_set"

This reverts the parts of commit
9816841 that have been split off into
PRs ocaml#383 and ocaml#386, as well as the Bottom stuff (likely to be unnecessary
as we're considering making `Coercion.compose` a total function).

Print aliases for debug.

Various improvements

* Use `Coercion.t` rather than `Coercion.t option` in many places
* Use `Rec_info.t` again where sensible (in making inlining decisions,
  for instance), but redefine it as `unit` pending the next phase of
  `Rec_info` overhaul
* Add simple `int` fields to `Coercion.t` for changing recursion depth;
  this is simpler than what we'll actually need but specific enough that
  we can test meaningfully (e.g., we can tell whether coercions are
  composed in the right order)

Address a CR

Update .depend

Overhaul Aliases_of_canonical_element; add Alias_set

Also return Bottom from more places (generally anything involved in a
meet).

Use Rec_info.unknown instead of unit

Add comments; simplify `Aliases` API a bit

Revert (most of) "Overhaul Aliases_of_canonical_element; add Alias_set"

This reverts the parts of commit
9816841 that have been split off into
PRs ocaml#383 and ocaml#386, as well as the Bottom stuff (likely to be unnecessary
as we're considering making `Coercion.compose` a total function).

Print aliases for debug.

Various improvements

* Use `Coercion.t` rather than `Coercion.t option` in many places
* Use `Rec_info.t` again where sensible (in making inlining decisions,
  for instance), but redefine it as `unit` pending the next phase of
  `Rec_info` overhaul
* Add simple `int` fields to `Coercion.t` for changing recursion depth;
  this is simpler than what we'll actually need but specific enough that
  we can test meaningfully (e.g., we can tell whether coercions are
  composed in the right order)

Address a CR

Update .depend

Overhaul Aliases_of_canonical_element; add Alias_set

Also return Bottom from more places (generally anything involved in a
meet).

Use Rec_info.unknown instead of unit

Add comments; simplify `Aliases` API a bit

Revert (most of) "Overhaul Aliases_of_canonical_element; add Alias_set"

This reverts the parts of commit
9816841 that have been split off into
PRs ocaml#383 and ocaml#386, as well as the Bottom stuff (likely to be unnecessary
as we're considering making `Coercion.compose` a total function).

…l#383)

* title case fix in up & running

* fix top level to toplevel for consistency & to match style guide

Signed-off-by: Christine Rose <professor.rose@gmail.com>