Remove all usage of the "register" storage class specifier.
diff --git a/shell/ash.c b/shell/ash.c
index c2e70a5..300f191 100644
--- a/shell/ash.c
+++ b/shell/ash.c
@@ -13472,7 +13472,7 @@
 
 static arith_t arith (const char *expr, int *perrcode)
 {
-    register char arithval; /* Current character under analysis */
+    char arithval; /* Current character under analysis */
     operator lasttok, op;
     operator prec;