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/drivers/net/r8169/r8169.c

@@ -128,7 +128,12 @@ struct rtl_desc {
 #define DESC_LS     0x10000000   // last fragment
 #define DESC_LEN    0x00003FFF
 
-#define NRX         32
+// 256, as the e1000 has. It was 32, and TCP advertises a 256 KB window --
+// some 180 full frames in flight -- which a gigabit link fills 32 slots with
+// in under half a millisecond. Everything past them was dropped, TCP read the
+// drops as congestion, and a download on the laptop crawled: apk sat on its
+// first index for minutes. The chip takes up to 1024.
+#define NRX         256
 #define NTX         32
 #define BUFSZ       2048         // one frame, with room for a VLAN tag