In Storable.xs, simplify and inline the macro STORE_HASH_SORT.

For 5.6.x and earlier, the interpreter context saving/restoring is not needed
prior to calling qsort(), as within the thread there is only one interpreter
in play.

Moreover, the SAVESPTR(orig_perl); in the removed code is not just pointless,
it's technically undefined behaviour. All that the SAVESPTR() macro will do
is ensure that the value of *(&orig_perl) is restored at scope exit. It
won't actually restore the interpreter context - that would need a call
to PERL_SET_CONTEXT with the value of origperl. The undefined behaviour is
because the LEAVE; which causes the scope pop action happens outside the
block, hence orig_perl has gone out of scope, and the address &orig_perl
(saved on the scope stack, written to by LEAVE), now points to invalid
memory. It is, however, quite hard to even get gcc's ASAN to trap this.

This code is likely unreachable anyway. It's only compiled in for 5.6.x and
earlier with USE_ITHREADS. ithreads was not useful until 5.8.0.

dist/Storable/Storable.xs

@@ -829,37 +829,6 @@ static void bless_retrieved(pTHX_ retrieve_cxt_t *retrieve_cxt, SV *sv, const ch
 #define BLESS(s,p)                                      \
         (bless_retrieved(aTHX_ retrieve_cxt, s, p))
 
-/*
- * sort (used in store_hash) - conditionally use qsort when
- * sortsv is not available ( <= 5.6.1 ).
- */
-
-#if (PATCHLEVEL <= 6)
-
-#if defined(USE_ITHREADS)
-
-#define STORE_HASH_SORT                                                 \
-        ENTER; {                                                        \
-                PerlInterpreter *orig_perl = PERL_GET_CONTEXT;          \
-                SAVESPTR(orig_perl);                                    \
-                PERL_SET_CONTEXT(aTHX);                                 \
-                qsort((char *)AvARRAY(av), len, sizeof(SV *), sortcmp); \
-        } LEAVE;
-
-#else /* ! USE_ITHREADS */
-
-#define STORE_HASH_SORT                                                 \
-        qsort((char *) AvARRAY(av), len, sizeof(SV *), sortcmp);
-
-#endif  /* USE_ITHREADS */
-
-#else /* PATCHLEVEL > 6 */
-
-#define STORE_HASH_SORT                         \
-        sortsv(AvARRAY(av), len, Perl_sv_cmp);  
-
-#endif /* PATCHLEVEL <= 6 */
-
 static void store(pTHX_ store_cxt_t *store_cxt, SV *sv);
 static SV *retrieve(pTHX_ retrieve_cxt_t *retrieve_cxt, const char *cname);
 
@@ -1469,9 +1438,7 @@ static void store_array(pTHX_ store_cxt_t *store_cxt, AV *av)
 static int
 sortcmp(const void *a, const void *b)
 {
-#if defined(USE_ITHREADS)
         dTHX;
-#endif /* USE_ITHREADS */
         return sv_cmp(*(SV * const *) a, *(SV * const *) b);
 }
 
@@ -1596,7 +1563,11 @@ static void store_hash(pTHX_ store_cxt_t *store_cxt, HV *hv)
 			av_store(av, AvFILLp(av)+1, key);	/* av_push(), really */
 		}
 
-		STORE_HASH_SORT;
+#if (PATCHLEVEL <= 6)
+		qsort((char *) AvARRAY(av), len, sizeof(SV *), sortcmp);
+#else
+		sortsv(AvARRAY(av), len, Perl_sv_cmp);  
+#endif
 
 		for (i = 0; i < len; i++) {
                         unsigned char flags = 0;