increase call_saved_regs[] in caller-save.c

[DJ Delorie]

I found this with the rl78-elf port...  can't guarantee it's not the
rl78 port itself, but the code does have two loops that fill the
array.

        * caller-save.c (setup_save_areas): Increase call_saved_regs[]
        size to avoid writing beyond the end of the array.  There are
        two loops that iterate over hard regs and potentially add to
        this array, so it must hold a max of 2x the hard regs.

Index: gcc/caller-save.c
===================================================================
--- gcc/caller-save.c   (revision 180758)
+++ gcc/caller-save.c   (working copy)
@@ -494,13 +494,13 @@ setup_save_areas (void)
     {
       rtx slot;
       char *saved_reg_conflicts;
       int next_k;
       struct saved_hard_reg *saved_reg2, *saved_reg3;
       int call_saved_regs_num;
-      struct saved_hard_reg *call_saved_regs[FIRST_PSEUDO_REGISTER];
+      struct saved_hard_reg *call_saved_regs[FIRST_PSEUDO_REGISTER*2];
       int best_slot_num;
       int prev_save_slots_num;
       rtx prev_save_slots[FIRST_PSEUDO_REGISTER];
 
       /* Find saved hard register conflicts.  */
       saved_reg_conflicts = (char *) xmalloc (saved_regs_num * saved_regs_num);