Fixes https://github.com/cesanta/mongoose-os/issues/394

CL: Fix buffer size passed to inet_ntop()

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E.g. if `ASSERT_EQ(myfunc(), 123)` fails, `myfunc()` would be invoked again to print the actual value.
This can cause confusion sometimes.
To avoid this, we cast arguments to double, which is wide enough for most cases and we provide a variant for 64 bit value types for when it's not.
We also perform a check and fail if argument to the check results in loss of precision.

CL: none

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CL: none

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Which is a replacement of (deprecated) `mg_http_parse_header`, but,
similarly to `asprintf`, allocates a new buffer if the client-provided
one is not large enough.

Also use it throughout mongoose code, and thus some header-related
limitations are removed; in particular,
https://github.com/cesanta/mongoose/issues/813 is fixed.

CL: Mongoose Web Server: Deprecate `mg_http_parse_header()` and implement `mg_http_parse_header2()` instead, which allocates a new buffer if the client-provided one is not large enough (similarly to `asprintf`).
CL: Mongoose Web Server: Fix limitations of header value lengths, e.g. when parsing authentication headers such as nonce, etc.

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CL: none

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To properly fail a test in a subroutine, return value needs to be passed up.
This snippet makes it short.

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In certain files it was necessary to make tests work from public
mongoose repo, so this commit makes things consistent.

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Even though it makes no prectical difference due to the way amalgamation works

CL: none

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CL: none

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CL: Mongoose Web Server: Remove tunneling functionality which was used by nobody

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CL: Mongoose Web Server: Publish sources and tests

Resolves https://github.com/cesanta/mongoose/issues/745

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