Initial commit: Schunix as it stands before the SchOS rename

An x86-64 operating system built from xv6, now largely rewritten: SMP,
a copy-on-write root filesystem (SchFS), PCI/USB/virtio drivers, a TTF
rasteriser, and a Linux-numbered syscall ABI.

No history before this point -- the tree was never under version control.
This commit exists so the rename that follows has something to undo to.

include/param.h

@@ -0,0 +1,28 @@
+#pragma once
+
+#define NPROC        128  // maximum number of processes
+#define KSTACKSIZE  4096  // size of per-process kernel stack (increased for x64)
+#define KSTACK_CANARY 0xDEADC0DEDEADC0DEULL  // sentinel at kstack[0], see kstack_check_canary()
+#define NCPU          16  // maximum number of CPUs
+#define NOFILE       128  // open files per process
+#define NFILE        512  // open files per system
+#define NINODE       200  // maximum number of active i-nodes
+#define NDEV          10  // maximum major device number
+#define RAMDISK_DEV    2  // memory-backed block device (kernel/dev/ramdisk.c)
+#define USBDISK_DEV    3  // USB mass storage (kernel/drivers/usb_storage.c)
+
+// Device the root filesystem is mounted from. Building with RAMROOT=1 defines
+// RAMDISK_ROOT and boots from the SCHFS image linked into the kernel instead
+// of the IDE disk, leaving the physical disk free to be reformatted from a
+// running system. See kernel/dev/ramdisk.c.
+#ifdef RAMDISK_ROOT
+#define ROOTDEV  RAMDISK_DEV
+#else
+#define ROOTDEV        1  // device number of file system root disk
+#endif
+#define MAXARG        32  // max exec arguments
+#define MAXPATH       128 // max path 
+#define MAXOPBLOCKS   30  // max # of blocks any FS op writes
+#define LOGSIZE      (MAXOPBLOCKS*3)  // max data blocks in on-disk log
+#define NBUF         (MAXOPBLOCKS*3)  // size of disk block cache
+#define FSSIZE       150000 // size of file system in blocks