format lex file

Docker 中安装gdb；
删除handler.h 文件；
BplusTree中的比较函数使用deps下公用接口；

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修复接收退出信号libevent没有正常退出循环的BUG

修复进程退出时，libevent 无法正常结束循环的BUG

* add windows-docker-tutorise
* add ccls-cache to gitignore

fix a typo in markdown

add a psql exit cmd for miniob

fix var len char

delete submodule path 

print prompt in client on platform without readline

fix defer's bug

fix a typo in docker command

implement some operators

remove unused variable

set response to failure while resolve failed

add copyright header info