tostring header value in socket compat

[leafo]

in luasocket you can pass a numeric value to a header and it sends it correctly as a string. With your compat library it will raise an error:

moon: ...leafo/.luarocks/share/lua/5.1/http/h1_connection.lua:399: field value invalid
stack traceback:
	[C]: in function 'assert'
	...leafo/.luarocks/share/lua/5.1/http/h1_connection.lua:399: in function 'write_header'
	...ome/leafo/.luarocks/share/lua/5.1/http/h1_stream.lua:689: in function 'write_headers'

I don't know where the appropriate place to fix this is, do you want to have the core library cast to string, or just have this fix as part of the compatibility layer?

In any case, I made a simple fix in the compatibility layer, but feel free to do your own solution.

[coveralls]

Coverage remained the same at 86.199% when pulling ac1d207 on leafo:master into 5e49a29 on daurnimator:master.

[daurnimator]

do you want to have the core library cast to string

No.

have this fix as part of the compatibility layer

this seems like the correct place.

---

However, I assume that the old code you're referring to is relying on implicit number=>string coercion? Keep in mind that the default "style" of numbers was never defined. In lua 5.3 floats will get a '.0'.

https://github.com/diegonehab/luasocket/blob/b9f6fd215a8f522733caedcb4d6d6b0c6e55103e/src/http.lua#L134

        h = (canonic[f] or f) .. ": " .. v .. "\r\n" .. h

Instead of calling tostring I'd like the exact same behaviour, i.e. use the .. operator. e.g.

   field = field .. "" -- coercion from number to string. the concat operator is right associative
   req.headers:append(name:lower(), field)

Also, please use my commit message style:

path(s)/affected: What I changed or fixed

Commentary on why this implementation was favoured over others.

Reference to issue #

[daurnimator]

Oh, and could you write a test to go with this PR?