Correct all relevant warnings found by the sparse semantic code analyzer. This include marking several symbols static...

Original commit message from CVS:
* gst/gstconfig.h.in:
* libs/gst/base/gstcollectpads.c: (gst_collect_pads_read_buffer):
* libs/gst/check/gstcheck.c: (gst_check_log_message_func),
(gst_check_log_critical_func), (gst_check_drop_buffers),
(gst_check_element_push_buffer_list):
* libs/gst/controller/gstcontroller.c: (gst_controller_get),
(gst_controller_get_type):
* libs/gst/controller/gsthelper.c: (gst_object_control_properties),
(gst_object_get_controller), (gst_object_get_control_source):
* libs/gst/controller/gstinterpolationcontrolsource.c:
(gst_interpolation_control_source_new):
* libs/gst/controller/gstlfocontrolsource.c:
(gst_lfo_control_source_new):
* libs/gst/dataprotocol/dataprotocol.c:
(gst_dp_event_from_packet_0_2):
* plugins/elements/gstfdsrc.c:
* plugins/elements/gstmultiqueue.c:
* plugins/elements/gsttee.c:
* plugins/elements/gsttypefindelement.c:
* plugins/indexers/gstfile...