Add claim support in plictool

JOURNAL.md

@@ -4311,3 +4311,34 @@ helpful.
 For that I need to first switch to the 8250/16550 driver. Let's try switch to
 the ttyS0 without enabling flow control yet. We probably need to change the
 stage1 and stage2 scripts to follow the proper console device.
+
+It works, but very slowly:
+
+    [    0.000000] Kernel command line: root=/dev/ram0 loglevel=7 rw earlycon=sbi console=ttyS0,115200n8 debug2 ...
+    ...
+    [   42.069358] Serial: 8250/16550 driver, 4 ports, IRQ sharing disabled
+    [   42.473860] of_serial 40001000.serial: error -ENXIO: IRQ index 0 not found
+    [   42.559263] printk: legacy console [ttyS0] disabled
+    [   42.614225] 40001000.serial: ttyS0 at MMIO 0x40001000 (irq = 0, base_baud = 3125000) is a 16550
+    [   42.645519] printk: legacy console [ttyS0] enabled
+    [   42.645519] printk: legacy console [ttyS0] enabled
+    [   42.656865] printk: legacy bootconsole [sbi0] disabled
+    [   42.656865] printk: legacy bootconsole [sbi0] disabled
+    [   42.896358] 40003000.serial: ttyS1 at MMIO 0x40003000 (irq = 1, base_baud = 3125000) is a 16550
+    [   42.999450] SuperH (H)SCI(F) driver initialized
+    ...
+    ~ # stty -a
+    speed 115200 baud;stty: standard input
+     line = 0;
+    intr = ^C; quit = ^\; erase = ^?; kill = ^U; eof = ^D; eol = <undef>;
+    eol2 = <undef>; swtch = <undef>; start = ^Q; stop = ^S; susp = ^Z; rprnt = ^R;
+    werase = ^W; lnext = ^V; flush = ^O; min = 1; time = 0;
+    -parenb -parodd -cmspar cs8 hupcl -cstopb cread clocal -crtscts
+    -ignbrk -brkint -ignpar -parmrk -inpck -istrip -inlcr -igncr icrnl ixon -ixoff
+    -iuclc -ixany -imaxbel -iutf8
+    opost -olcuc -ocrnl onlcr -onocr -onlret -ofill -ofdel nl0 cr0 tab0 bs0 vt0 ff0
+    isig icanon iexten echo echoe echok -echonl -noflsh -xcase -tostop -echoprt
+    echoctl echoke -flusho -extproc
+
+Let's add the ability to claim a context in the plictool, as I suspect the claim
+may be broken.