Make it compile with -Werror on gcc 4.6

public/common/unicode/unistr.h

 /*
 **********************************************************************
 *   Copyright (C) 1998-2010, International Business Machines
 *   Corporation and others.  All Rights Reserved.
 **********************************************************************
 *
 * File unistr.h
 *
 * Modification History:
 *
@@ skipping 4005 matching lines @@
 { return doReplace(start, _length, &srcChar, 0, 1); }
 
 inline UnicodeString&
 UnicodeString::replace(int32_t start,
                int32_t _length,
                UChar32 srcChar) {
   UChar buffer[U16_MAX_LENGTH];
   int32_t count = 0;
   UBool isError = FALSE;
   U16_APPEND(buffer, count, U16_MAX_LENGTH, srcChar, isError);
+  (void) isError;
   return doReplace(start, _length, buffer, 0, count);
 }
 
 inline UnicodeString&
 UnicodeString::replaceBetween(int32_t start,
                   int32_t limit,
                   const UnicodeString& srcText)
 { return doReplace(start, limit - start, srcText, 0, srcText.length()); }
 
 inline UnicodeString&
@@ skipping 283 matching lines @@
 inline UnicodeString&
 UnicodeString::append(UChar srcChar)
 { return doReplace(length(), 0, &srcChar, 0, 1); }
 
 inline UnicodeString&
 UnicodeString::append(UChar32 srcChar) {
   UChar buffer[U16_MAX_LENGTH];
   int32_t _length = 0;
   UBool isError = FALSE;
   U16_APPEND(buffer, _length, U16_MAX_LENGTH, srcChar, isError);
+  (void) isError;
   return doReplace(length(), 0, buffer, 0, _length);
 }
 
 inline UnicodeString&
 UnicodeString::operator+= (UChar ch)
 { return doReplace(length(), 0, &ch, 0, 1); }
 
 inline UnicodeString&
 UnicodeString::operator+= (UChar32 ch) {
   return append(ch);
@@ skipping 98 matching lines @@
 { return doReverse(0, length()); }
 
 inline UnicodeString&
 UnicodeString::reverse(int32_t start,
                int32_t _length)
 { return doReverse(start, _length); }
 
 U_NAMESPACE_END
 
 #endif