lzop: add overflow check

See CVE-2014-4607
http://www.openwall.com/lists/oss-security/2014/06/26/20

function                                             old     new   delta
lzo1x_decompress_safe                               1010    1031     +21

Change-Id: I98acf36d2474a722759cad25c31bf1c486c00e61
Signed-off-by: Denys Vlasenko <vda.linux@googlemail.com>