Revert "Make various primitives non_null_value (#2604)"

This reverts commit fd39aec.

Author: d-kalinichenko

ocaml/otherlibs/alpha/dune

@@ -39,7 +39,7 @@
 (rule
  (deps
   (glob_files ../stdlib_alpha/*.{ml,mli}))
- (targets alpha.ml alpha.mli or_null.ml or_null.mli)
+ (targets alpha.ml alpha.mli)
  (action
   (bash
    "cp ../stdlib_alpha/*.{ml,mli} .; mv stdlib_alpha.ml alpha.ml; mv stdlib_alpha.mli alpha.mli")))

ocaml/otherlibs/stdlib_alpha/or_null.ml

@@ -1 +0,0 @@
-module Or_null = Or_null

ocaml/otherlibs/stdlib_alpha/or_null.mli

@@ -1 +0,0 @@
-module Or_null = Or_null

ocaml/otherlibs/stdlib_alpha/stdlib_alpha.ml

@@ -90,7 +90,7 @@ Line 1, characters 9-33:
              ^^^^^^^^^^^^^^^^^^^^^^^^
 Error: This alias is bound to type 'a -> int
        but is used as an instance of type ('b : void)
-       The layout of 'a -> int is non_null_value, because
+       The layout of 'a -> int is value, because
          it's a function type.
        But the layout of 'a -> int must be a sublayout of void, because
          of the annotation on the type variable 'b.
@@ -104,7 +104,7 @@ Line 1, characters 27-31:
 1 | type t = 'a -> int as (_ : void)
                                ^^^^
 Error: Bad layout annotation:
-         The layout of 'a -> int is non_null_value, because
+         The layout of 'a -> int is value, because
            it's a function type.
          But the layout of 'a -> int must be a sublayout of void, because
            of the annotation on the wildcard _ at line 1, characters 27-31.

ocaml/otherlibs/stdlib_alpha/stdlib_alpha.mli

@@ -121,7 +121,7 @@ type r : void = {a:string}
 Line 1, characters 0-26:
 1 | type r : void = {a:string}
     ^^^^^^^^^^^^^^^^^^^^^^^^^^
-Error: The layout of type r is non_null_value, because
+Error: The layout of type r is value, because
          it's a boxed record type.
        But the layout of type r must be a sublayout of void, because
          of the annotation on the declaration of the type r.
@@ -133,7 +133,7 @@ type v : void = A of t_value
 Line 1, characters 0-28:
 1 | type v : void = A of t_value
     ^^^^^^^^^^^^^^^^^^^^^^^^^^^^
-Error: The layout of type v is non_null_value, because
+Error: The layout of type v is value, because
          it's a boxed variant type.
        But the layout of type v must be a sublayout of void, because
          of the annotation on the declaration of the type v.
@@ -145,7 +145,7 @@ type attr : void = ..
 Line 1, characters 0-21:
 1 | type attr : void = ..
     ^^^^^^^^^^^^^^^^^^^^^
-Error: The layout of type attr is non_null_value, because
+Error: The layout of type attr is value, because
          it's an extensible variant type.
        But the layout of type attr must be a sublayout of void, because
          of the annotation on the declaration of the type attr.
@@ -159,8 +159,8 @@ Line 1, characters 40-45:
                                             ^^^^^
 Error: This expression has type string but an expression was expected of type
          ('a : void)
-       The layout of string is non_null_value, because
-         it is the primitive non-null value type string.
+       The layout of string is value, because
+         it is the primitive value type string.
        But the layout of string must be a sublayout of void, because
          of the annotation on the type variable 'a.
 |}];;
@@ -187,7 +187,7 @@ Line 1, characters 40-45:
                                             ^^^^^
 Error: This expression has type 'b * 'c
        but an expression was expected of type ('a : void)
-       The layout of 'a * 'b is non_null_value, because
+       The layout of 'a * 'b is value, because
          it's a tuple type.
        But the layout of 'a * 'b must be a sublayout of void, because
          of the annotation on the type variable 'a.
@@ -206,7 +206,7 @@ Line 2, characters 36-37:
                                         ^
 Error: This expression has type [ `A of int | `B ]
        but an expression was expected of type 'a t = ('a : void)
-       The layout of [ `A of int | `B ] is non_null_value, because
+       The layout of [ `A of int | `B ] is value, because
          it's a polymorphic variant type.
        But the layout of [ `A of int | `B ] must be a sublayout of void, because
          of the definition of t at line 1, characters 0-22.
@@ -222,7 +222,7 @@ Line 2, characters 31-32:
                                    ^
 Error: This expression has type int -> int
        but an expression was expected of type 'a t = ('a : void)
-       The layout of int -> int is non_null_value, because
+       The layout of int -> int is value, because
          it's a function type.
        But the layout of int -> int must be a sublayout of void, because
          of the definition of t at line 1, characters 0-22.
@@ -248,7 +248,7 @@ Line 4, characters 17-39:
                      ^^^^^^^^^^^^^^^^^^^^^^
 Error: This expression has type (module X_int)
        but an expression was expected of type 'a t = ('a : void)
-       The layout of (module X_int) is non_null_value, because
+       The layout of (module X_int) is value, because
          it's a first-class module type.
        But the layout of (module X_int) must be a sublayout of void, because
          of the definition of t at line 1, characters 0-22.