Make every CORE compile with its respective language revision

This is a preparation work to assign language version to core classes.
I.e. PseudoStash.^ver would report back either `6.c` or `6.e` depending
from which CORE the class was imported.

src/Perl6/World.nqp

@@ -683,8 +683,12 @@ class Perl6::World is HLL::World {
             if nqp::eqat($!setting_name, 'NULL', 0) {
                 $*COMPILING_CORE_SETTING := 1;
                 $*SET_DEFAULT_LANG_VER := 0;
+                my $lang_ver := nqp::iseq_s($!setting_name, 'NULL')
+                                    ?? '6.c'
+                                    !! '6.' ~ nqp::substr($!setting_name, 5, 1);
+                nqp::getcomp('perl6').set_language_version: $lang_ver;
+
             }
-            # self.load_setting($/,$!setting_name);
             $*UNIT.annotate('IN_DECL', 'mainline');
         }
     }

src/core/Rakudo/Internals.pm6

@@ -15,6 +15,8 @@ my class X::Str::Sprintf::Directives::Count { ... }
 my class X::Str::Sprintf::Directives::Unsupported { ... }
 my class X::TypeCheck { ... }
 
+# Marker symbol for 6.c-mode regex boolification.
+my class Rakudo::Internals::RegexBoolification6cMarker { }
 
 my class Rakudo::Internals {
 
@@ -40,9 +42,6 @@ my class Rakudo::Internals {
         method dynamic() { False }
     }
 
-    # Marker symbol for 6.c-mode regex boolification.
-    class RegexBoolification6cMarker { }
-
     # rotate nqp list to another given list without using push/pop
     method RotateListToList(\from,\n,\to) {
         nqp::stmts(

src/core/core_prologue.pm6

@@ -9,6 +9,8 @@ my class Failure { ... }
 my class Rakudo::Deprecations { ... }
 my class Rakudo::Internals { ... }
 my class Rakudo::Internals::JSON { ... }
+my class Rakudo::Internals::RegexBoolification6cMarker { ... }
+my class Rakudo::Internals::HyperWorkBatch { ... }
 my class Rakudo::Iterator { ... }
 #?if !js
 my class ThreadPoolScheduler { ... }