locale.c: Don't ever use system LC_ALL

This fixes Perl#20231

LC_ALL is a compendium of the individual locale categories, such as
LC_CTYPE, LC_NUMERIC, ....  When all categories are in the same locale,
it acts just like an individual category.  But when the categories are
not in the same locale, some means must be used to indicate that.
Platforms differ in how they represent this.  Alpine uses:

    a;b;c;d;e;f

where each letter is replaced by the correct locale for a given
category.  Which category is in which position is deterministic, and
platform-specific.  Other platforms separate by a '/'.  And glibc uses a
more informative format:

    LC_CTYPE=a;LC_NUMBERIC=b; ...

This has the advantage that it's obvious to the reader what is what, and
the order in the string is irrelevant.

It might be possible, but painful, for a Configure probe to figure out
what the syntax is for the current platform.  I chose not to do that.  A
platform might come along with a novel syntax unanticipated by whatever
probe we came up with.

Instead, perl uses the glibc format internally, and when it needs to get
or set LC_ALL from the system, it loops through each category
individually, so that by the time it has done all of them, LC_ALL will
have been implicitly handled.

The breaking commit a7ff7ac failed to do that.

Author: khwilliamson

locale.c

@@ -4649,8 +4649,12 @@ Perl_init_i18nl10n(pTHX_ int printwarn)
 #  endif
 #  ifdef USE_PL_CURLOCALES
 
-    /* Initialize our records.  If we have POSIX 2008, we have LC_ALL */
-    void_setlocale_c(LC_ALL, porcelain_setlocale(LC_ALL, NULL));
+    /* Initialize our records. */
+    for (i = 0; i < NOMINAL_LC_ALL_INDEX; i++) {
+        (void) emulate_setlocale_i(i, porcelain_setlocale(categories[i], NULL),
+                                   RECALCULATE_LC_ALL_ON_FINAL_INTERATION,
+                                   __LINE__);
+    }
 
 #  endif