Mp4: fixed setting wrong mdat atom size in very rare cases. Atom size is the sum of atom header size and atom data size. The specification says that the first 4 bytes are set to one when the atom size is greater than the maximum unsigned 32-bit value. Which means atom header size should be considered when the comparison takes place between atom data size and 0xffffffff.

# Copyright (C) Igor Sysoev
# Copyright (C) Nginx, Inc.


    cat << END                                            >> $NGX_MAKEFILE

$NGX_LIBATOMIC/src/libatomic_ops.a:	$NGX_LIBATOMIC/Makefile
	cd $NGX_LIBATOMIC && \$(MAKE)

$NGX_LIBATOMIC/Makefile:	$NGX_MAKEFILE
	cd $NGX_LIBATOMIC \\
	&& if [ -f Makefile ]; then \$(MAKE) distclean; fi \\
	&& ./configure

END