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/elf.h

@@ -0,0 +1,35 @@
+#define ELF_MAGIC 0x464C457FU
+
+struct elfhdr {
+  uint32 magic;
+  uchar  elf[12];
+  uint16 type;
+  uint16 machine;
+  uint32 version;
+  uint64 entry;
+  uint64 phoff;
+  uint64 shoff;
+  uint32 flags;
+  uint16 ehsize;
+  uint16 phentsize;
+  uint16 phnum;
+  uint16 shentsize;
+  uint16 shnum;
+  uint16 shstrndx;
+};
+
+struct proghdr {
+  uint32 type;
+  uint32 flags;
+  uint64 off;
+  uint64 vaddr;
+  uint64 paddr;
+  uint64 filesz;
+  uint64 memsz;
+  uint64 align;
+};
+
+#define ELF_PROG_LOAD           1
+#define ELF_PROG_FLAG_EXEC      1
+#define ELF_PROG_FLAG_WRITE     2
+#define ELF_PROG_FLAG_READ      4