Add Proc::Async for Moar. Bumps NQP_REVISION.

Enables asynchronous spawning of a process, tapping of stdout or
stderr (or both) by bytes or chars, and provides a promise for
process completion that, if kept, gives a Proc::Status. Todo is
killing the process and async writes to stdin of that process.
Mention the use of --moar-option=--enable-jit
Proper --moar-option, spotted by japhb++
Naively fix RT #122514
Prevent using Bool:D as a Matcher for methods also
Make isnt a bit more verbose on failure, like is
Remove fossil from eval_dies_ok
Kill another fossil: no such thing as a bad death
Make (dies|lives)_ok also take nonCallable to EVAL
Use new tests for S26
S26: Change #| to create leading declaration comments
S26: Remove leading comments from codebase

Leading comments currently break the build process (but work
otherwise), and I don't have the knowhow to fix it.  I'm
guessing it has something to do with BOOTSTRAP
Rename docs to leading_docs
Track preceding declarations
Implement trailing docs

It's pretty rudimentary at the moment, but it's a start:

  - Uses strings instead of objects
  - Only deals with package declarations
  - Doesn't deal with trailing blocks
Implement leading declarative comments for parameters
Set up trailing docs with DOCEE
Add traits for applying trailing decl docs
Use trait application for trailing decl docs

Using HOW.set_trailing_docs works for classes, but it
breaks down for routines because they all share a single
HOW, resulting in every Routine sharing the same trailing
docs
Track line numbers for routine declarations

This is necessary to implement trailing declarative docs
for routines