Integrate IDE ATAPI and SCSI CD-ROM emulation

by Alexander Bezzubikov for QEMU

Currently the IDE ATAPI and SCSI CD-ROM emulated devices are two distinct implementations, and have different bugs/features. This leads to the situation that things which work when using the IDE emulation don't work when using the SCSI emulation and vice versa. So this project is for implementing a virtual ATA-to-SCSI bridge in QEMU, use this for emulating an IDE ATAPI drive, and merging the missing features from the IDE implementation into the SCSI one.