Correct several blunders in the timeout code, mostly my own fault (for

Correct several blunders in the timeout code, mostly my own fault (for
not testing it -- apparently test_timeout.py doesn't test anything
useful):

In internal_select():

- The tv_usec part of the timeout for select() was calculated wrong.

- The first argument to select() was one too low.

- The sense of the direction argument to internal_select() was
  inverted.

In PySocketSock_settimeout():

- The calls to internal_setblocking() were swapped.

Also, repaired some comments and fixed the test for the return value
of internal_select() in sendall -- this was in the original patch.