- Fix my_read/my_write to handle return values from read/write correctly
- Add debugging 'deprecated function' warning to my_lread/my_lwrite
- Add debugging 'error, read/write interrupt not handled' warning to my_quick_read/my_quick_write

There is no test case associated with these changes.  However, this is a conservative change,
and no repeatable test case is available.


mysys/my_lread.c:
  Warn about using deprecated function.
mysys/my_lwrite.c:
  Warn about using deprecated function.
mysys/my_pread.c:
  Handle interrupted read() or write() (EINTR) properly
mysys/my_quick.c:
  Warn about interrupted read() or write(), which is not
  handled by my_quick_read() or my_quick_write().
mysys/my_read.c:
  Handle interrupted read() (EINTR) properly
mysys/my_write.c:
  Handle interrupted write() (EINTR) properly