ww: import toolchain — C bootstrap + ww-side self-host (phases 0-10)

C bootstrap (phases 0-9):
  cmd/wwc, cmd/6c, cmd/6a, cmd/6l, cmd/ww, rt, lib/*.

ww-side self-host (phase 10):
  selfhost/cmd/wwc — ww-cgen frontend; bootstrap fixed point.
  selfhost/cmd/6a  — assembler; byte-identical to C 6a (test 991).
  selfhost/cmd/6l  — linker w/ archive (.a) support; byte-identical
                     to C 6l (test 992).
  selfhost/cmd/ww  — driver (build/run/version); byte-identical to
                     C ww (test 993).

make test: 15/15. make bootstrap: ww2.s == ww3.s, ww2.o == ww3.o,
ww2 == ww3 byte-identical, with the full ww-tooled chain.

lib/bytes/bytes.ww

@@ -0,0 +1,51 @@
+// bytes — slice operations over []u8.
+
+export fn equal(a: []u8, b: []u8) bool = {
+	let i: i32 = 0;
+	for (i < a.len) {
+		if (i >= b.len) { return false; };
+		if (a[i] != b[i]) { return false; };
+		i += 1;
+	};
+	return i == b.len;
+};
+
+export fn indexbyte(s: []u8, c: u8) i32 = {
+	let i: i32 = 0;
+	for (i < s.len) {
+		if (s[i] == c) { return i; };
+		i += 1;
+	};
+	return -1;
+};
+
+export fn copy(dst: []u8, src: []u8) i32 = {
+	let n: i32 = dst.len;
+	if (src.len < n) { n = src.len; };
+	let i: i32 = 0;
+	for (i < n) {
+		dst[i] = src[i];
+		i += 1;
+	};
+	return n;
+};
+
+// indexsub — first index of `sub` in `s`, or -1. Mirrors
+// strings.index but on []u8. Empty `sub` matches at 0.
+export fn indexsub(s: []u8, sub: []u8) i32 = {
+	if (sub.len == 0) { return 0; };
+	if (sub.len > s.len) { return -1; };
+	let last: i32 = s.len - sub.len;
+	let i: i32 = 0;
+	for (i <= last) {
+		let j: i32 = 0;
+		let ok: bool = true;
+		for (j < sub.len) {
+			if (s[i + j] != sub[j]) { ok = false; j = sub.len; }
+			else { j += 1; };
+		};
+		if (ok) { return i; };
+		i += 1;
+	};
+	return -1;
+};