修复NSTextAlignmentCenter引起的警告
#ifdef __IPHONE_6_0 // iOS6 and later
# define UITextAlignmentCenter NSTextAlignmentCenter
# define UITextAlignmentLeft NSTextAlignmentLeft
# define UITextAlignmentRight NSTextAlignmentRight
# define UILineBreakModeTailTruncation NSLineBreakByTruncatingTail
# define UILineBreakModeMiddleTruncation NSLineBreakByTruncatingMiddle
#endif