locale.c: Rename variable

This was shadowing an outer variable, and conflating two things.  We are
looking for the UTF8ness of some strings in a locale to try to divine if
the locale itself is a UTF-8 one or not.  But we're doing this in the
context of trying to find the CODESET of the locale, like 8859-1 or
UTF-8..  And the utf8ness of the CODESET name is always going to be an
ASCII string.  Thus there are two types of utf8ness being looked at
here, and the names of the variables for each should be distinct.

locale.c

@@ -6299,7 +6299,7 @@ S_my_langinfo_i(pTHX_
          * For non-English locales or non-dollar currency locales, we likely
          * will find out whether a locale is UTF-8 or not */
 
-        utf8ness_t is_utf8 = UTF8NESS_UNKNOWN;
+        utf8ness_t strings_utf8ness = UTF8NESS_UNKNOWN;
         char * scratch_buf = NULL;
 
 #          if defined(USE_LOCALE_MONETARY) && defined(HAS_LOCALECONV)
@@ -6320,7 +6320,7 @@ S_my_langinfo_i(pTHX_
         if ((PL_langinfo_recursed & LANGINFO_RECURSED_MONETARY) == 0) {
             PL_langinfo_recursed |= LANGINFO_RECURSED_MONETARY;
             (void) my_langinfo_c(CRNCYSTR, LC_MONETARY, locale, &scratch_buf,
-                                 NULL, &is_utf8);
+                                 NULL, &strings_utf8ness);
             PL_langinfo_recursed &= ~LANGINFO_RECURSED_MONETARY;
         }
 
@@ -6336,7 +6336,7 @@ S_my_langinfo_i(pTHX_
 #             endif
 
         /* If we have ruled out being UTF-8, no point in checking further. */
-        if (   is_utf8 != UTF8NESS_NO
+        if (   strings_utf8ness != UTF8NESS_NO
             && (PL_langinfo_recursed & LANGINFO_RECURSED_TIME) == 0)
         {
             /* But otherwise do check more.  This is done even if the currency
@@ -6375,18 +6375,18 @@ S_my_langinfo_i(pTHX_
                                      NULL, &this_is_utf8);
                 Safefree(scratch_buf);
                 if (this_is_utf8 == UTF8NESS_NO) {
-                    is_utf8 = UTF8NESS_NO;
+                    strings_utf8ness = UTF8NESS_NO;
                     break;
                 }
 
                 if (this_is_utf8 == UTF8NESS_YES) {
-                    is_utf8 = UTF8NESS_YES;
+                    strings_utf8ness = UTF8NESS_YES;
                 }
             }
             PL_langinfo_recursed &= ~LANGINFO_RECURSED_TIME;
 
-            /* Here we have gone through all the LC_TIME elements.  is_utf8 has
-             * been set as follows:
+            /* Here we have gone through all the LC_TIME elements.
+             * strings_utf8ness has been set as follows:
              *      UTF8NESS_NO           If at least one isn't legal UTF-8
              *      UTF8NESS_IMMMATERIAL  If all are ASCII
              *      UTF8NESS_YES          If all are legal UTF-8 (including
@@ -6401,7 +6401,7 @@ S_my_langinfo_i(pTHX_
         /* If nothing examined above rules out it being UTF-8, and at least one
          * thing fits as UTF-8 (and not plain ASCII), assume the codeset is
          * UTF-8. */
-        if (is_utf8 == UTF8NESS_YES) {
+        if (strings_utf8ness == UTF8NESS_YES) {
             retval = "UTF-8";
             break;
         }