Keep track of if collation locale is UTF-8 or not

This will be used in future commits

embedvar.h

@@ -168,6 +168,7 @@
 #define PL_in_clean_objs	(vTHX->Iin_clean_objs)
 #define PL_in_eval		(vTHX->Iin_eval)
 #define PL_in_load_module	(vTHX->Iin_load_module)
+#define PL_in_utf8_COLLATE_locale	(vTHX->Iin_utf8_COLLATE_locale)
 #define PL_in_utf8_CTYPE_locale	(vTHX->Iin_utf8_CTYPE_locale)
 #define PL_incgv		(vTHX->Iincgv)
 #define PL_initav		(vTHX->Iinitav)

intrpvar.h

@@ -245,6 +245,7 @@ PERLVAR(I, exit_flags,	U8)		/* was exit() unexpected, etc. */
 
 PERLVAR(I, utf8locale,	bool)		/* utf8 locale detected */
 PERLVAR(I, in_utf8_CTYPE_locale, bool)
+PERLVAR(I, in_utf8_COLLATE_locale, bool)
 #ifdef USE_LOCALE_CTYPE
     PERLVAR(I, warn_locale, SV *)
 #endif

locale.c

@@ -485,6 +485,7 @@ Perl_new_collate(pTHX_ const char *newcoll)
       is_standard_collation:
 	PL_collxfrm_base = 0;
 	PL_collxfrm_mult = 2;
+        PL_in_utf8_COLLATE_locale = FALSE;
 	return;
     }
 
@@ -498,6 +499,8 @@ Perl_new_collate(pTHX_ const char *newcoll)
             goto is_standard_collation;
         }
 
+        PL_in_utf8_COLLATE_locale = _is_cur_LC_category_utf8(LC_COLLATE);
+
 	{
             /* A locale collation definition includes primary, secondary,
              * tertiary, etc. weights for each character.  To sort, the primary

sv.c

@@ -14789,6 +14789,7 @@ perl_clone_using(PerlInterpreter *proto_perl, UV flags,
     /* Did the locale setup indicate UTF-8? */
     PL_utf8locale	= proto_perl->Iutf8locale;
     PL_in_utf8_CTYPE_locale = proto_perl->Iin_utf8_CTYPE_locale;
+    PL_in_utf8_COLLATE_locale = proto_perl->Iin_utf8_COLLATE_locale;
     /* Unicode features (see perlrun/-C) */
     PL_unicode		= proto_perl->Iunicode;