unget doesn't respect binary/text mode

[daurnimator]

socket:unget doesn't respect binary/text mode

Test case:

local cs = require "cqueues.socket"
local c, s = cs.pair()
s:xwrite('hi\r\nthere\nworld\r', "n")
local foo = c:read(-99999)
c:unget(foo)
local bar = c:read(-99999)
assert(foo == bar)

[daurnimator]

remember to regen the pdf when you merge this one.