Bug fixes, documentation, and NEC PC-98 development

• A reminder regarding an October 2016 release: VGA240.EXE no longer prints "INT 10h hooked" nor clears the screen.
• Cleanup of the make system
• 8237 (DMA), 8259 (PIC), 8254 (PIT) updates for PC-9801/PC-9821 targets. Tested working on actual hardware.
• PCI library PC-9821 support, though with extra code to handle a rather unfortunate shortcoming when probing PCI slots with no devices in it. Tested working on actual hardware.
• ZIP4DOS tool, for generating ZIP archives intended specifically for MS-DOS (where InfoZIP is inadequate for the task). Character set conversion is available so that files on the host, in UTF-8 encoding, can be encoded for the target MS-DOS system (CP437 for USA MS-DOS or CP932 for Japanese PC-9801 MS-DOS). ZIP spanning is available, in which each "span" is emitted as a 1.44MB floppy disk image that you write to a floppy that then appears as a valid spanning archive to MS-DOS releases of PKUNZIP 2.x.
• More work on Win386 VXD header defs.
• Mouse driver for Windows 1.0 through Windows ME that allows "guest pointer integration" with DOSBox-X if the DOSBox Integrated Device is enabled. The integration allows interacting with Windows using the mouse without having to "capture" the mouse, and it makes it possible to operate the guest Windows system with your laptop/tablet touchscreen.