Keyboard lights, TLB shootdowns, battery in sysfs, /proc/pid/maps

Caps, Num and Scroll Lock now light their LEDs on PS/2 and USB keyboards,
share one state between keyboards, and stop toggling on key repeat. X sets
them through evdev writes while it holds the keyboard.

Unmapping memory in a process with threads on other CPUs now flushes their
TLBs with an IPI. Without it a freed page stayed reachable through stale
translations, which corrupted Epiphany's heap on SMP.

ACPI batteries and AC adapters appear under /sys/class/power_supply.
/proc/<pid>/maps lists file mappings, and a process killed by a fault
names the file and offset it died in. r8169 gets a 256-entry RX ring.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01S1giNvrHTrPMPw7V6x1kQ4

kernel/arch/x86_64/lapic.c

@@ -581,3 +581,19 @@ void cmostime(struct rtcdate *r)
   *r = t1;
   r->year += 2000;
 }
+
+// A fixed interrupt to one processor, by APIC id. Waits for the local APIC
+// to say it has sent the last one before writing the next: two ICR writes
+// back to back lose the first.
+void
+lapic_send_ipi(int apicid, int vector)
+{
+  if (!lapic)
+    return;
+  while (lapic[ICRLO] & DELIVS)
+    ;
+  lapicw(ICRHI, apicid << 24);
+  lapicw(ICRLO, vector);                // fixed, physical, edge, no shorthand
+  while (lapic[ICRLO] & DELIVS)
+    ;
+}