move $? to Perl5::Terms

lib/Perl5/Actions.nqp

@@ -1483,10 +1483,6 @@ class Perl5::Actions is HLL::Actions does STDActions {
         $V5DEBUG && say("special_variable:sym<\$.>($/)");
     }
 
-    method special_variable:sym<$?>($/) {
-        $V5DEBUG && say("special_variable:sym<\$?>($/)");
-    }
-
     method name($/) {
         $V5DEBUG && say("name($/)"); }
 

lib/Perl5/English.pm

@@ -13,6 +13,8 @@ sub EXPORT(|) {
         use v5;
         $ex{'$SUBSCRIPT_SEPARATOR'} = $;; # XXX do binding instead of assignment
         $ex{'$SUBSEP'}              = $;;
+        $ex{'$OUTPUT_AUTOFLUSH'}    = $|;
+        $ex{'$CHILD_ERROR'}         = $?;
     }
     %ex
 }

lib/Perl5/Grammar.nqp

@@ -2318,10 +2318,6 @@ grammar Perl5::Grammar is HLL::Grammar does STD5 {
         <sym> | '$INPUT_LINE_NUMBER' | '$NR'
     }
 
-    token special_variable:sym<$?> {
-        <sym> | '$CHILD_ERROR'
-    }
-
     token special_variable:sym<${ }> {
         <!before { 1; }>
     }

lib/Perl5/Terms.pm

@@ -11,6 +11,7 @@ my $OUTPUT_AUTOFLUSH_P    := Proxy.new(
     FETCH => method ()   { $OUTPUT_AUTOFLUSH },
     STORE => method ($n) { $OUTPUT_AUTOFLUSH = $n; try $*OUT.autoflush( ?$n ); } # XXX there is no IO::Handle.autoflush (yet)
 );
+my $CHILD_ERROR            = 0;
 
 sub EXPORT(|) {
     my %ex;
@@ -20,6 +21,7 @@ sub EXPORT(|) {
     %ex<$]>                       := $VERSION_FLOAT;
     %ex<$;>                       := $SUBSCRIPT_SEPARATOR;
     %ex<$|>                       := $OUTPUT_AUTOFLUSH_P;
+    %ex<$?>                       := $CHILD_ERROR;
 
     # Because Perl6 already has variables like $/ and $! built in, we can't ex-/import them directly.
     # So we need an accessor, the grammar token '$/' can use, and a way to support the English module.