Add a pattern scan function similar to the one recently added to
GstAdapter, and a unit test (based on the adapter one).
Fixes#585592.
API: add gst_byte_reader_masked_scan_uint32()
Original commit message from CVS:
* docs/libs/gstreamer-libs-sections.txt:
* libs/gst/base/gstbytereader.c: (gst_byte_reader_get_data),
(gst_byte_reader_peek_data):
* libs/gst/base/gstbytereader.h:
* win32/common/libgstbase.def:
API: Add gst_byte_reader_get_data and gst_byte_reader_peek_data
to get a pointer to the data at the current position and have
a guaranteed size.