Cherry pick 2 more patches from the upstream

source/common/ucasemap.cpp

 // Copyright (C) 2016 and later: Unicode, Inc. and others.
 // License & terms of use: http://www.unicode.org/copyright.html
 /*
 *******************************************************************************
 *
 *   Copyright (C) 2005-2016, International Business Machines
 *   Corporation and others.  All Rights Reserved.
 *
 *******************************************************************************
 *   file name:  ucasemap.cpp
@@ skipping 182 matching lines @@
     return destIndex;
 }
 
 static inline int32_t
 appendUChar(uint8_t *dest, int32_t destIndex, int32_t destCapacity, UChar c) {
     int32_t length=U8_LENGTH(c);
     if(length>(INT32_MAX-destIndex)) {
         return -1;  // integer overflow
     }
     int32_t limit=destIndex+length;
-    if(limit<destCapacity) {
+    if(limit<=destCapacity) {
         U8_APPEND_UNSAFE(dest, destIndex, c);
     }
     return limit;
 }
 
 static inline int32_t
 appendString(uint8_t *dest, int32_t destIndex, int32_t destCapacity,
              const uint8_t *s, int32_t length) {
     if(length>0) {
         if(length>(INT32_MAX-destIndex)) {
@@ skipping 537 matching lines @@
 U_CAPI int32_t U_EXPORT2
 ucasemap_utf8FoldCase(const UCaseMap *csm,
                       char *dest, int32_t destCapacity,
                       const char *src, int32_t srcLength,
                       UErrorCode *pErrorCode) {
     return ucasemap_mapUTF8(csm,
                    (uint8_t *)dest, destCapacity,
                    (const uint8_t *)src, srcLength,
                    ucasemap_internalUTF8Fold, pErrorCode);
 }