[RUTNIME] Support C++ RPC

[FrozenGene]

C++ RPC is very useful for embedded devices, which can not have Python environment easily. And thanks @siju-samuel ' great work, based on #1756, we could get C++ RPC work on these embedded devices. I want to summary some different places compared that PR.

• The users could only use libtvm_runtime, doesn't need to link libtvm. This requirement is the same as deployment.
• Previous PR could not work well and process can not exist normally. We write one method named as waitpid_eintr to handle it, we also modify the incorrect argument from --timeout to -timeout.
• Fix the logic of GetCmdOption. Previous PR can not work well like --key=mtk6763, which will recognize the second k.
• Fix the logic of GetPath. In our python api, we could add one argument to specify where we would like to place the deployed .so

Others small changes are not listed.

The screenshot of work example:

Device:

Server:

Better to do:
Modify the runtime code and cpp_rpc code to be C++03 compatible.

@tqchen @siju-samuel @snowolfhawk @yzhliu

[tqchen]

@weberlo @srkreddy1238 @snowolfhawk it would be great if you can also help to review the PR

[FrozenGene]

@tqchen Wish I have solved many comments. I also replace SelectHelper into PoolHelper.

Remained:
Ideally, we should just use std::istringstream to do the validation(to reduce memory complexity). Given that this is a util function, we would like to apply such higher standard
-> Split internally is used istringstream to do things in fact, need to make sure the meaning.

[tqchen]

split then check creates additional data structures such as vector and string(additional data structures), which can be avoided as you can simply do istringstream to parse the ints (check the bits) and avoid creation of additional containers

[FrozenGene]

split then check creates additional data structures such as vector and string(additional data structures), which can be avoided as you can simply do istringstream to parse the ints (check the bits) and avoid creation of additional containers

@tqchen When I implement completely, I find using system api inet_pton is a better solution, we could add ipv6 check too.

[tqchen]

+1 for ipv6 compatibility

[tqchen]

some final nits

[weberlo]

A few very minor nits. Otherwise, LGTM.

[FrozenGene]

@tqchen @weberlo I should resolve all the comments. Please review again.

[tqchen]

some final nits

[FrozenGene]

@tqchen Have resolved LOG(ERROR) -> LOG(FATAL) and gnulib issue. Please review again

[tqchen]

Thanks @FrozenGene @weberlo !