v0.3.1: --dump-offsets tool + NOTICE.md per module

The README has been claiming "each module credits the original CVE
reporter and PoC author in its NOTICE.md" since v0.1.0, but only
copy_fail_family actually shipped one. Fixed.

  modules/<name>/NOTICE.md (×19 new + 1 existing): per-module
    research credit covering CVE ID, discoverer, original advisory
    URL where public, upstream fix commit, IAMROOT's role.

  iamroot.c: new --dump-offsets subcommand. Resolves kernel offsets
    via the existing core/offsets.c four-source chain (env →
    /proc/kallsyms → /boot/System.map → embedded table), then emits
    a ready-to-paste C struct entry for kernel_table[]. Run once
    as root on a target kernel build; upstream via PR. Eliminates
    fabricating offsets — every shipped entry traces back to a
    `iamroot --dump-offsets` invocation on a real kernel.

  docs/OFFSETS.md: documents the --dump-offsets workflow.
  CVES.md: notes the NOTICE.md convention + offset dump tool.

  iamroot.c: bump IAMROOT_VERSION 0.3.0 → 0.3.1.

modules/af_packet_cve_2017_7308/NOTICE.md

@@ -0,0 +1,29 @@
+# NOTICE — af_packet (CVE-2017-7308)
+
+## Vulnerability
+
+**CVE-2017-7308** — AF_PACKET TPACKET_V3 integer overflow in
+`tp_block_size * tp_block_nr` → heap write-where via sendmmsg spray.
+
+## Research credit
+
+Discovered by **Andrey Konovalov** (Google), March 2017. A research-era
+classic — Konovalov found multiple AF_PACKET bugs in this campaign.
+
+Original advisory + writeup:
+<https://googleprojectzero.blogspot.com/2017/05/exploiting-linux-kernel-via-packet.html>
+
+Upstream fix: mainline 4.11 / stable 4.10.6 (March 2017).
+Branch backports: 4.10.6 / 4.9.18 / 4.4.57 / 3.18.49.
+
+## IAMROOT role
+
+x86_64-only. Userns gives CAP_NET_RAW; `socket(AF_PACKET, SOCK_RAW)`
++ TPACKET_V3 with overflowing tp_block_size triggers the integer
+overflow + heap spray via 200 raw skbs on lo. Best-effort cred-race
+finisher (64 child workers polling geteuid). Offset table covers
+Ubuntu 16.04/4.4 and 18.04/4.15; other kernels via the
+`IAMROOT_AFPACKET_OFFSETS` env var.
+
+`--full-chain` engages the shared modprobe_path finisher with
+stride-seeded sk_buff data-pointer overwrite.