human68k: actually, the comm field coming from the OS is in ph68kdos_comline format, so use it accordingly

rtl/human68k/h68kdos.inc

@@ -92,7 +92,7 @@ type
   Th68kdos_startup = record
     mcb: pbyte;
     bss_end: pbyte;
-    comm: pbyte;
+    comm: ph68kdos_comline;
     environ: pbyte;
     entry: pbyte;
     intr: pbyte;

rtl/human68k/system.pp

@@ -150,11 +150,11 @@ begin
   inquotes:=false;
   inarg:=false;
 
-  p:=pchar(h68k_startup.comm);
+  p:=@h68k_startup.comm^.buffer;
   if not assigned(p) then
     exit;
 
-  argl:=length(p);
+  argl:=h68k_startup.comm^.len;
   if argl < 1 then
     argl:=1;