Stop leaking tempcells from extra args in bltin

===============> cat leak.sh
#/bin/sh

# Monitor awk's memory consumption while repeatedly calling int()
# with extra, tempcell-producing expression arguments. There is
# nothing special about int(). Most of the other functions in
# run.c/bltin() will do.

${1:-./a.out} '
BEGIN {
	mem = "ps -p $PPID -o rsz="
	system(mem)
	while (++i <= 100000) {
		int(1+2, 3+4, 5+6, 7+8, 9+0)
		if (i % 10000 == 0)
			system(mem)
	}
}
' 2>/dev/null
===============> paste <(./leak.sh ./master.out) <(./leak.sh ./a.out)
 2404	 2520
 4612	 2528
 6804	 2528
 9000	 2528
11192	 2528
13384	 2528
15580	 2528
17772	 2528
19968	 2528
22160	 2528
24356	 2528

1 files changed, 4 insertions, 2 deletions

diff --git a/run.c b/run.c
index 7ea6590..cf0d5ee 100644
--- a/run.c
+++ b/run.c
@@ -1712,8 +1712,10 @@ Cell *bltin(Node **a, int n)	/* builtin functions. a[0] is type, a[1] is arg lis
 	setfval(x, u);
 	if (nextarg != NULL) {
 		WARNING("warning: function has too many arguments");
-		for ( ; nextarg; nextarg = nextarg->nnext)
-			execute(nextarg);
+		for ( ; nextarg; nextarg = nextarg->nnext) {
+			y = execute(nextarg);
+			tempfree(y);
+		}
 	}
 	return(x);
 }