generalize parsing to allow extensions to add arbitrary syntax; add 'proc' keyword to introduce a routine.

examples/factorial.csn

@@ -1,10 +1,10 @@
 (
-    (main
+    (proc main
         (call fac 5)
         (ld r0 res0)
         (halt)
     )
-    (fac
+    (proc fac
         (cmp arg0 2
             (eq? (ret 2)))
         (sub r0 arg0 1)

examples/screen_bounce.csn

@@ -1,10 +1,10 @@
 ; Set log level to "info" or above for the best results!
 
 (
-    (main
+    (proc main
         (sc-init 800 600)
-        (sc-opt 1 0) ; auto blit
-        (sc-opt 2 60) ; frame rate
+        (sc-opt 1 1) ; auto blit
+        (sc-opt 2 25) ; frame rate
 
         (ld r0 5) ; x
         (ld r1 0) ; y
@@ -15,16 +15,12 @@
         (ld r5 0x3300ff)
 
         (:loop)
-        (add r5 0x000001)
-        (and r5 0xffffff)
-        (sc-px r0 r1 r5)
-        (add r0 r2)
-        (add r1 r3)
-        (cmp r0 799 (eq? (ld r2 -1)))
-        (cmp r0 0 (eq? (ld r2 1)))
-        (cmp r1 599 (eq? (ld r3 -1)))
-        (cmp r1 0 (eq? (ld r3 1)))
-        (sc-blit 0)
+            (add r5 0x000001)
+            (sc-px r0 r1 r5)
+            (add r0 r2)
+            (add r1 r3)
+            (cmp r0 799 (eq? (ld r2 -1)) (ne? (cmp r0 0 (eq? (ld r2 1)))))
+            (cmp r1 599 (eq? (ld r3 -1)) (ne? (cmp r1 0 (eq? (ld r3 1)))))
         (j :loop)
     )
 )