Fix per-instance Regexp timeout
This makes it follow what was decided in [Bug #19055]:
* `Regexp.new(str, timeout: nil)` should respect the global timeout
* `Regexp.new(str, timeout: huge_val)` should use the maximum value that
can be represented in the internal representation
* `Regexp.new(str, timeout: 0 or negative value)` should raise an error
I updated the patch with documentation but forgot about it,
earlier :x
[ruby-core:88616] [Misc #15014]
git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/trunk@64535 b2dd03c8-39d4-4d8f-98ff-823fe69b080e
Relying on "struct timespec" was too annoying API-wise and
used more stack space. "double" was a bit wacky w.r.t rounding
in the past, so now we'll switch to using a 64-bit type.
Unsigned 64-bit integer is able to give us over nearly 585
years of range with nanoseconds. This range is good enough
for the Linux kernel internal time representation, so it
ought to be good enough for us.
This reduces the stack usage of functions while GVL is held
(and thus subject to marking) on x86-64 Linux (with ppoll):
rb_wait_for_single_fd 120 => 104
do_select 120 => 88
[ruby-core:88582] [Misc #15014]
git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/trunk@64533 b2dd03c8-39d4-4d8f-98ff-823fe69b080e
