ASAN leaves a pointer to the fake frame on the stack; we can use the
__asan_addr_is_in_fake_stack API to work out the extent of the fake
stack and thus mark any VALUEs contained therein.

[Bug #20001]

This reverts commit d10bc3a2b8300cffc383e10c3730871e851be24c.

ASAN leaves a pointer to the fake frame on the stack; we can use the
__asan_addr_is_in_fake_stack API to work out the extent of the fake
stack and thus mark any VALUEs contained therein.

[Bug #20001]

Our current implementation of rb_postponed_job_register suffers from
some safety issues that can lead to interpreter crashes (see bug #1991).
Essentially, the issue is that jobs can be called with the wrong
arguments.

We made two attempts to fix this whilst keeping the promised semantics,
but:
  * The first one involved masking/unmasking when flushing jobs, which
    was believed to be too expensive
  * The second one involved a lock-free, multi-producer, single-consumer
    ringbuffer, which was too complex

The critical insight behind this third solution is that essentially the
only user of these APIs are a) internal, or b) profiling gems.

For a), none of the usages actually require variable data; they will
work just fine with the preregistration interface.

For b), generally profiling gems only call a single callback with a
single piece of data (which is actually usually just zero) for the life
of the program. The ringbuffer is complex because it needs to support
multi-word inserts of job & data (which can't be atomic); but nobody
actually even needs that functionality, really.

So, this comit:
  * Introduces a pre-registration API for jobs, with a GVL-requiring
    rb_postponed_job_prereigster, which returns a handle which can be
    used with an async-signal-safe rb_postponed_job_trigger.
  * Deprecates rb_postponed_job_register (and re-implements it on top of
    the preregister function for compatability)
  * Moves all the internal usages of postponed job register
    pre-registration

Introduce Universal Parser mode for the parser.
This commit includes these changes:

* Introduce `UNIVERSAL_PARSER` macro. All of CRuby related functions
  are passed via `struct rb_parser_config_struct` when this macro is enabled.
* Add CI task with 'cppflags=-DUNIVERSAL_PARSER' for ubuntu.

The socket extensions rubysocket.h pulls in the "private" include/gc.h,
which now depends on vm_core.h. vm_core.h pulls in id.h

when tool/update-deps generates the dependencies for the makefiles, it
generates the line for id.h to be based on VPATH, which is configured in
the extconf.rb for each of the extensions. By default VPATH does not
include the actual source directory of the current Ruby so the
dependency fails to resolve and linking fails.

We need to append the topdir and top_srcdir to VPATH to have the
dependancy picked up correctly (and I believe we need both of these to
cope with in-tree and out-of-tree builds).

I copied this from the approach taken in
https://github.com/ruby/ruby/blob/master/ext/objspace/extconf.rb#L3

Split `PACKED_STRUCT` and `PACKED_STRUCT_UNALIGNED` macros into the
macros bellow:
* `RBIMPL_ATTR_PACKED_STRUCT_BEGIN`
* `RBIMPL_ATTR_PACKED_STRUCT_END`
* `RBIMPL_ATTR_PACKED_STRUCT_UNALIGNED_BEGIN`
* `RBIMPL_ATTR_PACKED_STRUCT_UNALIGNED_END`