Ensure that exiting thread invokes end-of-life behaviour. (#10039)

	Fix exception handling in `rb_fiber_scheduler_set`. (#10042)

	Don't clear pending interrupts in the parent process. (#10365)

There's an exhaustive explanation of this in the linked redmine bug, but
the short version is as follows:

blocking_region_begin can spill callee-saved registers to the stack for
its own use. That means they're not saved to ec->machine by the call to
setjmp, since by that point they're already on the stack and new,
different values are in the real registers. ec->machine's end-of-stack
pointer is also bumped to accomodate this, BUT, after
blocking_region_begin returns, that points past the end of the stack!

As far as C is concerned, that's fine; the callee-saved registers are
restored when blocking_region_begin returns. But, if another thread
triggers GC, it is relying on finding references to Ruby objects by
walking the stack region pointed to by ec->machine.

If the C code in exec; subsequently does things that use that stack
memory, then the value will be overwritten and the GC might prematurely
collect something it shouldn't.

[Bug #20493]

	Fix `Thread#join(timeout)` when running inside the fiber scheduler.
	 (#7903)

	---
	 test/fiber/test_thread.rb | 22 ++++++++++++++++++++++
	 thread.c                  |  5 +++++
	 2 files changed, 27 insertions(+)

	Only emit circular dependency warning for owned thread shields [Bug
	 #19415]

	If multiple threads attemps to load the same file concurrently
	it's not a circular dependency issue.

	So we check that the existing ThreadShield is owner by the current
	fiber before warning about circular dependencies.
	---
	 internal/thread.h                                     |  1 +
	 load.c                                                |  3 ++-
	 spec/ruby/core/kernel/shared/require.rb               | 11 +++++++++++
	 spec/ruby/fixtures/code/concurrent_require_fixture.rb |  4 ++++
	 test/ruby/test_require.rb                             |  3 ---
	 thread.c                                              | 11 +++++++++++
	 6 files changed, 29 insertions(+), 4 deletions(-)
	 create mode 100644 spec/ruby/fixtures/code/concurrent_require_fixture.rb

	Use Thread.pass until thread.stop? to wait for thread to block

	[Bug #19415]

	It should be more reliable
	---
	 spec/ruby/fixtures/code/concurrent_require_fixture.rb | 2 +-
	 1 file changed, 1 insertion(+), 1 deletion(-)

A patch from katsu (Katsuhiro Ueno)

[Bug #19110]

* Ensure that blocked fibers don't prevent valid wakeups.