Update jnr-posix.jar for new error method
JRUBY-6136: Changing jnr-posix to use errno() value unconditionally has created lots of failures in windows (take one)
Update for next jnr-posix which has fstat() support for windows
Fix #645 by calling Java Math.cbrt directly.

Related rubyspec change: https://github.com/rubyspec/rubyspec/pull/206
Return -∞ for -0.0
Merge pull request #658 from tychobrailleur/gamma_zero

Math.gamma should return -∞ for -0.0
Update RubySpec to 80bb145.
Fix Array#delete return value in 1.8 mode.
Fix (non-)tainting of single-element Array#join with tainted sep.
Also passing due to Array#join fix.
Fix two Array#to_s/inspect encoding issues and add minor optz.
Move BasicObject constant up from Object to BasicObject.
These are passing now.
Fix div of 0.0 error and clean up comparison tags (no bug number).
Untag some passing IO.for_fd specs.
Untag passing Time specs.
Untag passing Struct specs.
Untag passing 1.8 mode String specs.
Untag passing 1.9-mode Regexp specs.
Tidy up Rational#** tags for hangs and tag slow #round spec.