Added get_revision and device_info

[botev]

Sorry, this should have been part of the previous, but was a bit busy.
One caveat is that I assumed that the commit string is truly static, so I return Cow<'static, str>. Also, I notice that the name of the platform has underscores Intel(R)_Core(TM)_i7-4600U_CPU_@ 2.10GHz so the question is should those be replaced by spaces or kept like that.

[9prady9]

@botev Commit string is a compile time string and the user should not free it. What does Cow<> do when a variable of such type goes out of scope ?

@pavanky Why does the platform name returned by af_device_info has underscores?

[pavanky]

@9prady9

@pavanky Why does the platform name returned by af_device_info has underscores?

I don't know what you mean. Can you show me an example ?

[9prady9]

@pavanky

Name: GeForce_GT_650M

Thats the output of af_devie_info for platform name, white spaces are replaced by underscores.

Edit:
You can also find it in the PR description for Intel CPU.

We are doing that at this line in the upstream.

[pavanky]

@9prady9 That is not platform name, that is device name. I don't remember why I changed spaces to underscores. If we are going to change this, it should probably change upstream.

[9prady9]

Okay. @botev No need to change underscores to white spaces.

[botev]

@9prady9 Cow is a clone-on-write smart pointer. Additionally, it relies on a reference. This means:

1. It does not free anything underlying (as in rust references require that the owner outlives them, but they do not free resources).
2. If someone decides to modify it in any way it clones the underlying object. E.g. if someone decides to use the returned value in building a new string it will clone it so that it does not modify the initial underlying string.

I think that is good consistent behavior and has 0 overhead at runtime (I think the modification checks are at compile time).