kill off remaining kgio uses

kgio is an extra download and shared object which costs users
bandwidth, disk space, startup time and memory.  Ruby 2.3+
provides `Socket#accept_nonblock(exception: false)' support
in addition to `exception: false' support in IO#*_nonblock
methods from Ruby 2.1.

We no longer distinguish between TCPServer and UNIXServer as
separate classes internally; instead favoring the `Socket' class
of Ruby for both.  This allows us to use `Socket#accept_nonblock'
and get a populated `Addrinfo' object off accept4(2)/accept(2)
without resorting to a getpeername(2) syscall (kgio avoided
getpeername(2) in the same way).

The downside is there's more Ruby-level argument passing and
stack usage on our end with HttpRequest#read_headers (formerly
HttpRequest#read).  I chose this tradeoff since advancements in
Ruby itself can theoretically mitigate the cost of argument
passing, while syscalls are a high fixed cost given modern CPU
vulnerability mitigations.

Note: no benchmarks have been run since I don't have a suitable
system.

1 files changed, 1 insertions, 1 deletions

diff --git a/test/unit/test_stream_input.rb b/test/unit/test_stream_input.rb
index 2a14135..7986ca7 100644
--- a/test/unit/test_stream_input.rb
+++ b/test/unit/test_stream_input.rb
@@ -9,7 +9,7 @@ class TestStreamInput < Test::Unit::TestCase
     @rs = "\n"
     $/ == "\n" or abort %q{test broken if \$/ != "\\n"}
     @env = {}
-    @rd, @wr = Kgio::UNIXSocket.pair
+    @rd, @wr = UNIXSocket.pair
     @rd.sync = @wr.sync = true
     @start_pid = $$
   end