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/dirty_pipe_cve_2022_0847/NOTICE.md

@@ -0,0 +1,21 @@
+# NOTICE — dirty_pipe
+
+## Vulnerability
+
+**CVE-2022-0847** — pipe `PIPE_BUF_FLAG_CAN_MERGE` flag inheritance allows
+arbitrary file write into the page cache.
+
+## Research credit
+
+Discovered and disclosed by **Max Kellermann** (CM4all GmbH), March 2022.
+
+Original advisory: <https://dirtypipe.cm4all.com/>
+
+Upstream fix: mainline 5.17 (commit `9d2231c5d74e`, Feb 2022).
+
+## IAMROOT role
+
+This module bundles the canonical splice-into-pipe primitive that
+writes UID=0 into `/etc/passwd`'s page cache, then drops a root shell
+via `su`. Detection covers the splice() syscall against sensitive
+files and non-root modifications to passwd/shadow.