[Crash-utility] [PATCH] Add -C option for search

Hello Dave, I add a new option -C for sub-command search to display memory contents just before and after the search target. The number of the memory unit displayed is specified by -C. for example, crash> search -p -C 3 dddd 17b5100: dddddddddddddddd dddddddddddddddd dddddddddddddddd 17b5118: dddd cdcdcdcdcdcdcdcd cdcdcdcdcdcdcdcd 17b5130: cdcdcdcdcdcdcdcd -- 85d04f818: 29 ffff88085d04f818 ffffea001d3f7e30 85d04f830: dddd 1000 ffff88085b48a000 85d04f848: ffff880876383b80 -- 8752cfec8: ddd9 dddb dddb 8752cfee0: dddd dddd dddf 8752cfef8: dddf -- 8752cfed0: dddb dddb dddd 8752cfee8: dddd dddf dddf 8752cff00: dde1 -- crash> Thanks. Zhang Yanfei