Remove GstPollMode from the API, it does not make sense to let the application contro...

Remove GstPollMode from the API, it does not make sense to let the application control this.

Original commit message from CVS:
Patch by: Ole André Vadla Ravnås
<ole dot andre dot ravnas at tandberg dot com>
* docs/gst/gstreamer-sections.txt:
* gst/gstpoll.c: (find_index), (gst_poll_free_winsock_event),
(gst_poll_update_winsock_event_mask), (gst_poll_new),
(gst_poll_free), (gst_poll_fd_init), (gst_poll_add_fd_unlocked),
(gst_poll_remove_fd), (gst_poll_fd_ctl_write),
(gst_poll_fd_ctl_read_unlocked), (gst_poll_fd_has_closed),
(gst_poll_fd_has_error), (gst_poll_fd_can_read_unlocked),
(gst_poll_fd_can_write), (gst_poll_wait),
(gst_poll_set_controllable), (gst_poll_restart),
(gst_poll_set_flushing):
* gst/gstpoll.h:
* libs/gst/net/gstnetclientclock.c: (gst_net_client_clock_new):
* libs/gst/net/gstnettimeprovider.c: (gst_net_time_provider_start),
(gst_net_time_provider_new):
* plugins/elements/gstfdsink.c: (gst_fd_sink_start):
* plugins/elements/gstfdsrc.c: (gst_fd_src_start):
* tests/benchmarks/gstpollstress.c: (main):
* tests/check/gst/gstpoll.c: (GST_START_TEST), (gst_poll_suite):
Remove GstPollMode from the API, it does not make sense to let the
application control this.
Add support for Win32.
Fix the testsuite. Fixes #520671.