Fixed functions that return messages in ?socket.c.

Moved complexity of connect and accept there.
Created a new options.c module to take care of options.
Auxiliar.c is now cleaner.

test/testclnt.lua

@@ -378,6 +378,19 @@ function connect_timeout()
     c:close()
 end
 
+------------------------------------------------------------------------
+function rebind_test()
+    local c = socket.bind("localhost", 0)
+    local i, p = c:getsockname()
+    local s, e = socket.tcp()
+    assert(s, e)
+    s:setoption("reuseaddr", false)
+    r, e = s:bind("localhost", p)
+    assert(not r, "managed to rebind!")
+    assert(e == "address already in use")
+    print("ok")
+end
+
 ------------------------------------------------------------------------
 test("method registration")
 test_methods(socket.tcp(), {
@@ -416,6 +429,9 @@ test_selectbugs()
 test("empty host connect: ")
 empty_connect()
 
+test("rebinding: ")
+rebind_test()
+
 test("active close: ")
 active_close()