Got the VM up and running! Augmented the documentation.

* src/*.[ch]:  Replaced the remaining `SCM_MAKINUM', and changed `SCM_VELTS'
  into `scm_vector_elements ()'.
* src/vm_loader.c (link):  Fixed so that it pushed a variable object on
  the stack.
* src/vm_system.c (variable-ref):  Fixed so that it uses `scm_variable_ref ()'
  and friends.
* module/system/vm/assemble.scm (dump-object!):  Fixed the string case.
* src/vm_engine.h (CONS):  Use `scm_cons' instead of `SCM_NEWCELL'.
* doc/guile-vm.texi:  Added actual instruction definitions, explanations of
  the program invocation mechanism, programs' object tables, etc., in the
  `Instruction Set' chapter.

git-archimport-id: lcourtes@laas.fr--2004-libre/guile-vm--revival--0.6--patch-5

src/vm_engine.h

@@ -130,10 +130,20 @@
   vp->fp = fp;					\
 }
 
-#define CACHE_PROGRAM()				\
-{						\
-  bp = SCM_PROGRAM_DATA (program);		\
-  objects = SCM_VELTS (bp->objs);		\
+/* Get a local copy of the program's "object table" (i.e. the vector of
+   external bindings that are referenced by the program), initialized by
+   `load-program'.  */
+#define CACHE_PROGRAM()					\
+{							\
+  size_t _vsize;					\
+  ssize_t _vincr;					\
+  scm_t_array_handle _vhandle;				\
+							\
+  bp = SCM_PROGRAM_DATA (program);			\
+  /* Was: objects = SCM_VELTS (bp->objs); */		\
+  objects = scm_vector_elements (bp->objs, &_vhandle,	\
+				 &_vsize, &_vincr);	\
+  scm_array_handle_release (&_vhandle);			\
 }
 
 #define SYNC_BEFORE_GC()			\
@@ -208,12 +218,8 @@
 
 #define CONS(x,y,z)				\
 {						\
-  SCM cell;					\
   SYNC_BEFORE_GC ();				\
-  SCM_NEWCELL (cell);				\
-  SCM_SET_CELL_OBJECT_0 (cell, y);		\
-  SCM_SET_CELL_OBJECT_1 (cell, z);		\
-  x = cell;					\
+  x = scm_cons (y, z);				\
 }
 
 #define POP_LIST(n)				\