Copy qtmux from revision 148 of the gst-qtmux repository.

Copy qtmux from revision 148 of the gst-qtmux repository.

Original commit message from CVS:
patch by: Thiago Sousa Santos <thiagossantos@gmail.com>
* configure.ac:
* gst/quicktime/Makefile.am:
* gst/quicktime/atoms.c:
* gst/quicktime/atoms.h:
* gst/quicktime/descriptors.c:
* gst/quicktime/descriptors.h:
* gst/quicktime/fourcc.h:
* gst/quicktime/ftypcc.h:
* gst/quicktime/gstqtmux.c:
* gst/quicktime/gstqtmux.h:
* gst/quicktime/gstqtmuxmap.c:
* gst/quicktime/gstqtmuxmap.h:
* gst/quicktime/properties.c:
* gst/quicktime/properties.h:
Copy qtmux from revision 148 of the gst-qtmux repository.
Fixes #550280.