The attached patch fixes leaking a Plumbmsg when saving a file
via Put in acme.

<snip>
To reproduce the problem:

	> open acme and determine its PID (let's assume it is 181451)

	cpu% leak -s 181451
	src(0x002000cb); // 1

	> modify a file in acme an middle click on 'Put'

	cpu% leak -s 181451
	src(0x002000cb); // 1
	src(0x0020ebbc); // 1
	src(0x0020ebcb); // 1
	src(0x0020ebdd); // 1
	src(0x0020ebf0); // 1
	src(0x0020ec1e); // 1
	src(0x0020ec39); // 1
	cpu% acid 181451
	/proc/181451/text:amd64 plan 9 executable
	/sys/lib/acid/port
	/sys/lib/acid/amd64
	acid: src(0x0020ebbc)
	/sys/src/cmd/acme/exec.c:678
	 673				f->text[i]->w->putseq = f->seq;
	 674				f->text[i]->w->dirty = w->dirty;
	 675			}
	 676		}
	 677		if(plumbsendfd >= 0){
	>678			pm = emalloc(sizeof(Plumbmsg));
	 679			pm->src = estrdup("acme");
	 680			pm->dst = estrdup("put");
	 681			pm->wdir = estrdup(name);
	 682			if(p = strrchr(pm->wdir, '/'))
	 683				*p = '\0';
	acid:

This patch ensures to always free the heap allocated Plumbsg.

After applying the patch the leak is fixed:

	> open acme and determine its PID (let's assume it is 181781)

	cpu% leak -s 181781
	src(0x002000cb); // 1

	> modify a file in acme an middle click on 'Put'

	cpu% leak -s 181781
	src(0x002000cb); // 1
	cpu%

The leak is not observed anymore by `leak`.
---
diff ca73f673473457152d6f1b2e9030495f8dec5c49 5c955e081f444e16d208b1ba78fe742a8f0a53c7
--- a/sys/src/cmd/acme/exec.c	Mon Nov  1 18:07:28 2021
+++ b/sys/src/cmd/acme/exec.c	Fri Nov  5 12:27:07 2021
@@ -687,8 +687,7 @@
 		pm->ndata = strlen(pm->data);
 		if(pm->ndata < messagesize-1024)
 			plumbsend(plumbsendfd, pm);
-		else
-			plumbfree(pm);
+		plumbfree(pm);
 	}
 	fbuffree(s);
 	fbuffree(r);
</snap>

The patch is attached for review.

Cheers,
Igor