fix aggressive loop optimizations

Previously, aggressive loop optimizations with a new compiler were not
possible due to undefined behaviour at end of arrays.

A macro "UBFIX" is added to allow ifdefs for fixes which resolve
undefined behavior. For example newer GCC versions will detect various
bugs in the original game code and will otherwise not compile with -Werror.

src/easy_chat.c

@@ -5273,12 +5273,17 @@ void InitEasyChatPhrases(void)
             gSaveBlock1Ptr->mail[i].words[j] = 0xFFFF;
     }
 
+#ifndef UBFIX
     // BUG: This is supposed to clear 64 bits, but this loop is clearing 64 bytes.
     // However, this bug has no resulting effect on gameplay because only the
     // Mauville old man data is corrupted, which is initialized directly after
     // this function is called when starting a new game.
     for (i = 0; i < 64; i++)
         gSaveBlock1Ptr->additionalPhrases[i] = 0;
+#else
+    for (i = 0; i < ARRAY_COUNT(gSaveBlock1Ptr->additionalPhrases); i++)
+        gSaveBlock1Ptr->additionalPhrases[i] = 0;
+#endif
 }
 
 static bool8 sub_811F28C(void)