Fix some spelling mistakes in comments:
refernce  ==> reference
happnes  ==> happens
threhold  ==> threshold
splitted  ==> split
mached  ==> matched
Signed-off-by: NZheng Yongjun <zhengyongjun3@huawei.com>
Signed-off-by: NMiklos Szeredi <mszeredi@redhat.com>