Revised text for references to portable support for C "int"

Those two files have suffered lots of changes, including the spin-off
of nativetypes, which no longers says anything like what was reported
in this issue. There seems to be no equivalent issue in the remaining
documentation, so this closes #1771

Once again, this kinda proves a couple of things
* We need a review tool that tells us, when we modify a file, if there
  are any outstanding issues on that file.
* Old issues need to be addressed, or they stagnate and become
  irrelevant. Also increasingly difficult to address, due to long
  conversations and need to dig up what they were *actually* about.

doc/Language/nativecall.pod6

@@ -29,7 +29,8 @@ that you can do is just adding to this simple pattern of declaring a Perl 6 sub
 naming it after the symbol you want to call and marking it with the "native"
 trait.
 
-You will also need to declare and use native types. Please check L<the native types page|/language/nativetypes> for more information.
+You will also need to declare and use native types. Please check
+L<the native types page|/language/nativetypes> for more information.
 
 =head1 Changing names
 
@@ -79,8 +80,8 @@ routine itself.
     use NativeCall;
     sub input_box() returns Str is encoded('utf8') is native('gui') { * }
 
-Note that a NULL string pointer can be passed by passing the Str type
-object; a NULL return will also be represented by the type object.
+Note that a C<NULL> string pointer can be passed by passing the Str type
+object; a C<NULL> return will also be represented by the type object.
 
 If the C function requires the lifetime of a string to exceed the function
 call, the argument must be manually encoded and passed as C<CArray[uint8]>:

doc/Language/nativetypes.pod6

@@ -145,7 +145,9 @@ valid type, you can use it in expressions:
      say $nothing.perl; # OUTPUT: «NativeCall::Types::void␤»
 
 In practice, it is an C<Uninstantiable> type that can rarely be used by itself,
-and in fact it is L<explicitly forbidden in C<return> types|/language/nativecall#Passing_and_returning_values>. However, it is
+and in fact it is
+L<explicitly forbidden in C<return> types|/language/nativecall#Passing_and_returning_values>.
+However, it is
 generally found in typed pointers representing the equivalent to the C<void *>
 pointer in C.