Fix/suppress warnings when building with gcc-8

src/main.c

@@ -85,7 +85,14 @@ void EnableVCountIntrAtLine150(void);
 
 void AgbMain()
 {
-    RegisterRamReset(MODERN ? RESET_ALL & ~RESET_IWRAM : RESET_ALL);
+#if MODERN
+    // Modern compilers are liberal with the stack on entry to this function,
+    // so RegisterRamReset may crash if it resets IWRAM.
+    RegisterRamReset(RESET_ALL & ~RESET_IWRAM);
+    DmaFill32(3, 0, IWRAM_START, 0x7E00);
+#else
+    RegisterRamReset(RESET_ALL);
+#endif //MODERN
     *(vu16 *)BG_PLTT = 0x7FFF;
     InitGpuRegManager();
     REG_WAITCNT = WAITCNT_PREFETCH_ENABLE | WAITCNT_WS0_S_1 | WAITCNT_WS0_N_3;