Add header-only Meson support

[Tachi107]

This allows users to call dependency('httplib') and have the include directory automatically configured.

This doesn't add any advanced functionality (as you can see by the diff) so there's nothing to maintain (unless you move httplib.h in a separate directory; in that case include_directories('.') should be changed to include_directories('newdir')). In fact, it only makes users' life simpler :)

[yhirose]

@Tachi107, thank you for your pull request, but I am probably not taking it... Please see this comment.

[Tachi107]

Yep I saw it, but this is to allow Meson users to use the project more easily, it doesn't change the repo's workflow

[Tachi107]

It works like this: users can add this repo as a git submodule in a folder called subprojects, and when they want to use this project they can simply add dependency('httplib') to the list of dependencies of their executable/build target.

executable(
  'my-program',
  sources: 'main.cpp',
  dependencies: dependency('httplib')
)

[yhirose]

@Tachi107, thanks for the comment. Please see the former discussion about the current CMake support, so that you would understand what I was trying to say.

As for CMake, I don't touch it at all, but @sum01 has been kindly and faithfully maintaining it for me up till now when any requests or problem reports come. Likewise, if you would like to accept the same responsibility regarding the Meson support, I am glad to merge it. Please let me know your answer.

Thanks for your understanding!

[Tachi107]

I implemented only the bare minimum, so it wouldn't be hard to maintain; happy to accept the responsibility :)

Before merging I have a question though, how should the project be called? "cpp-httplib" or "httplib"?

[yhirose]

@Tachi107, great! I chose "cpp-????" as cmake project names in other cpp projects (cpp-peglib, cpp-fstlib and so on). But the current CMakeLists.txt maintained by @sum01 sets the project name to "httplib". So you can pick either one, since I don't have a strong opinion about it. :)
Please let me know when you think the pr is ready to merge.

[Tachi107]

I prefer "cpp-httplib" as it is the same name as the repo, and makes Meson's automatic fallback work without issues.

Ready to merge!

[yhirose]

I have just merged it. Thanks for the fine contribution!