mg.c: Add asserts

These two switch() statements handle magic names.  We now have a quick
way to determine if the first character of a name is magic.  Assert that
the cases of the switch match.  This will tell us if something gets
out-of-sync.

Author: khwilliamson

mg.c

@@ -906,6 +906,9 @@ Perl_magic_get(pTHX_ SV *sv, MAGIC *mg)
     }
 
     nextchar = *remaining;
+
+    assert(generic_isCC_(*mg->mg_ptr, CC_MAGICAL_));
+
     switch (*mg->mg_ptr) {
     case '\001':		/* ^A */
         if (SvOK(PL_bodytarget)) sv_copypv(sv, PL_bodytarget);
@@ -3016,6 +3019,8 @@ Perl_magic_set(pTHX_ SV *sv, MAGIC *mg)
         return 0;
     }
 
+    assert(generic_isCC_(*mg->mg_ptr, CC_MAGICAL_));
+
     switch (*mg->mg_ptr) {
     case '\001':	/* ^A */
         if (SvOK(sv)) sv_copypv(PL_bodytarget, sv);