Implement string constants, buffers, macro barriers

macro barriers are a hack to say "this form does its own macroexpansion
internally" so that we can have state-smart macros that expand to
different values depending on if they are being used in code or in a
function definition. This seems like a real bad design choice but I
can't think of a better one right now!

(not quite true: the better design choice is to allow forms to return
opgens, and then define a :bytes form that returns the address of the
generated thing. :bytes could be understood by :buffer directly.
But that's... complicated.)

neutgs/init.fnl

@@ -17,11 +17,11 @@
     5                   0x0100  ; desk manager
     9                   0x0100) ; ADB
 
-  (asm pascalhex (db 5) hexbuf (bytes "     "))
+  (buffer hexbuf (cstr "    "))
 
   (fn printnum (num)
     (long! (ref hexbuf) (HexIt num))
-    (WriteString (far-ref pascalhex)))
+    (WriteCString (far-ref hexbuf)))
 
   (asm event-buffer)
   (global word event-what)

ssc/iigs/u2-debug.fnl

@@ -22,15 +22,24 @@
          (sec) (xce))) ; re-enter emulation mode
 
   (require ssc.stdlib)
+  (require ssc.iigs.toolbox)
   (require ssc.iigs.uthernet2)
 
+  (macro out [#(! (WriteLine (far-ref (pstr [$2]))))])
+
+  (buffer hexbuf (cstr "    "))
+  (fn printnum (num)
+    (long! (ref hexbuf) (HexIt num))
+    (WriteCString (far-ref hexbuf)))
+  
   (global word u2-debug-server-connected 0)
   (fn u2-init-debug-server ()
+    (out "Starting server")
     (u2-reset)
     (u2-udp-server-start 6502)
     (set! u2-debug-server-connected 0))
 
-  (asm u2-debug-buffer (bytes [(string.rep "\x00" 1500)]))
+  (buffer u2-debug-buffer 1500)
 
   (predef-fn u2-debug-server-poll () void far)
 
@@ -83,6 +92,7 @@
       (when (> size 0)
         (let (msgid (u2-read)
               cmd (u2-read))
+            (printnum msgid) (out "Got message!")
           (u2-read-buf (ref u2-debug-buffer) (- size 2))
           (u2-rx-complete)
           (when (not u2-debug-server-connected)
@@ -91,6 +101,8 @@
           (u2-debug-server-cmd msgid cmd)))))
 
   (fn debug-server-loop ()
+    (TextStartUp)
+    (IMStartUp)
     (u2-init-debug-server)
     (while true (u2-debug-server-poll)))
 )