rework the vm support for wide strings

* libguile/_scm.h (SCM_OBJCODE_MINOR_VERSION): Bump.

* libguile/vm-engine.c (vm_error_bad_wide_string_length): New error
  case.

* libguile/vm-i-loader.c (load-unsigned-integer, load-integer)
  (load-keyword): Remove these instructions. The former two are
  obsoleted by make-int64/make-uint64, the latter via make-keyword.
  (load-string): Only handle narrow strings.
  (load-symbol): Only handle narrow symbols. The wide case is handled
  via make-symbol.
  (load-wide-string): New instruction, for wide strings.

* libguile/vm-i-system.c (define): Move here from loaders.c, as now it
  just takes a sym on the stack.
  (make-keyword, make-symbol): New instructions.

* module/language/assembly.scm: Remove removed instructions. No more
  width byte in load-string etc.

* module/language/assembly/compile-bytecode.scm (write-bytecode): Adapt
  to change in instruction set.

* module/language/glil/compile-assembly.scm (glil->assembly): Compile
  define by pushing the sym then emitting (define).
  (dump-object): Dump narrow and wide strings differently. Use
  make-keyword and make-symbol as appropriate.

* module/language/tree-il/compile-glil.scm (flatten): When compiling a
  ref to a primitive (not a call), first see if the primitive is
  actually bound in the root module. (That's not the case with e.g.
  bytevector-u8-ref).

* module/system/xref.scm (program-callee-rev-vars): Don't parse out
  "nexts".

* test-suite/tests/asm-to-bytecode.test ("compiler"): Adapt to bytecode
  format change.

module/language/assembly/compile-bytecode.scm

@@ -65,11 +65,13 @@
     (write-byte (logand (ash x -8) 255))
     (write-byte (logand (ash x -16) 255))
     (write-byte (logand (ash x -24) 255)))
-  (define (write-uint32 x) (case byte-order
-                             ((1234) (write-uint32-le x))
-                             ((4321) (write-uint32-be x))
-                             (else (error "unknown endianness" byte-order))))
+  (define (write-uint32 x)
+    (case byte-order
+      ((1234) (write-uint32-le x))
+      ((4321) (write-uint32-be x))
+      (else (error "unknown endianness" byte-order))))
   (define (write-wide-string s)
+    (write-loader-len (* 4 (string-length s)))
     (string-for-each (lambda (c) (write-uint32 (char->integer c))) s))
   (define (write-loader-len len)
     (write-byte (ash len -16))
@@ -133,14 +135,11 @@
                ;; `scm_c_make_objcode_slice ()'.
                (write-bytecode meta write get-addr '()))))
         ((make-char32 ,x) (write-uint32-be x))
-        ((load-unsigned-integer ,str) (write-loader str))
-        ((load-integer ,str) (write-loader str))
         ((load-number ,str) (write-loader str))
-        ((load-string ,str) (write-sized-loader str))
-        ((load-symbol ,str) (write-sized-loader str))
-        ((load-keyword ,str) (write-sized-loader str))
+        ((load-string ,str) (write-loader str))
+        ((load-wide-string ,str) (write-wide-string str))
+        ((load-symbol ,str) (write-loader str))
         ((load-array ,bv) (write-bytevector bv))
-        ((define ,str) (write-sized-loader str))
         ((br ,l) (write-break l))
         ((br-if ,l) (write-break l))
         ((br-if-not ,l) (write-break l))