[etr/libhttpserver] Initial integration

[sgbhat2]

This PR adds files for initial integration of etr/libhttpserver

Currently working on adding fuzz targets to libhttpserver etr/libhttpserver#213
The fuzz target was able to point this bug etr/libhttpserver@bcd12d3

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[google-cla]

Thanks for your pull request. It looks like this may be your first contribution to a Google open source project (if not, look below for help). Before we can look at your pull request, you'll need to sign a Contributor License Agreement (CLA).

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[sgbhat2]

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[jonathanmetzman]

We generally like to know how critical projects are before accepting them into OSS-Fuzz.
Could you help us here since I've never heard of this project?
Are there many users of libhttpserver?
Who are some of the users of libhttpserver?
Are there any large companies using it for example?
Is it used in any high profile embedded settings?

[sgbhat2]

Thanks to @etr for the list.

Many dependent projects fetch libhttpserver from toolchains. Few known popular use cases are listed below:

• IntelAI's nnpi card and Broadcom's stblinux include libhttpserver in its toolchain.
• Buildroot includes libhttpserver in its toolchain, so many embedded projects fetch libhttpserver directly using buildroot and it is provided in many OSes for embedded applications by multiple companies. (Home-assistant, SmartCam, Openil, Qtoggleos, Cxcore)
• libhttpserver is also used in non-embedded projects like proxysql and larger.
• Yahoo (Verizon) also uses it as part of their Turnitas modules : tunitas-scarpet and tunitas-tarwater.
• Some linux distros also provide it as a package (Fedora, ArchLinux) and it is ported to MacOS through HomeBrew.