Breaking: deprecate safe-buffer.Buffer calls

[ChALkeR]

safe-buffer.Buffer function/constructor is just a re-export of buffer.Buffer and should be deprecated likewise.

Otherwise, using Buffer = require('safe-buffer').Buffer magically hides the deprecation message, which it shouldn't, as that code will actually cause runtime deprecation errors on Node.js >= 10.

In fact, ecosystem analysis shows that people do that a lot to silence standard linter — they see a recommendation to use safe-buffer in the warning, they throw in var Buffer = require('buffer').Buffer, the warning goes away, nothing actually changes.
Example:

• webdriverio/webdriverio@05cbd31#diff-124380949022817b90b622871837d56cR31 (a module with 548 759 downloads/month),
• and there are more of those.

Also, even if they migrate to the new API and install safe-buffer for the actual polyfills, the fact that that line alone disables the deprecation message makes them overlook calls to the old API.
Examples:

• max-mapper/websocket-stream@c9312bd (218 288 d/m, fix in Avoid using deprecated Buffer constructor max-mapper/websocket-stream#142),
• serialport/node-serialport@e8d9d2b (113 138 d/m, fix in Avoid using deprecated Buffer constructor serialport/node-serialport#1510),
• karma-runner/karma@3d94b8c (3 973 193 d/m, fix in Avoid using deprecated Buffer constructor karma-runner/karma#2947),
• and there are more of those.

Old Buffer API is going to be runtime-deprecated in Node.js 10.0 (nodejs/node#19079) and require('safe-buffer').Buffer(arg) actually hits that deprecated API, so this change is needed for developers to spot those issues that would soon become runtime warnings, in advance. eslint-plugin-node was already helping developers to spot that deprecated Buffer API usage in advance, but only until they put Buffer = require('safe-buffer').Buffer into their code (and they do that a lot, since that's the recommended way to keep older Node.js versions support).

Actually, I am not even sure if this should be a breaking or a bugfix change. Thoughts?

/cc @Trott, @feross .

[codecov-io]

Codecov Report

Merging #110 into master will increase coverage by <.01%.
The diff coverage is 100%.

@@            Coverage Diff             @@
##           master     #110      +/-   ##
==========================================
+ Coverage   98.21%   98.21%   +<.01%     
==========================================
  Files          43       43              
  Lines        1065     1066       +1     
==========================================
+ Hits         1046     1047       +1     
  Misses         19       19

Impacted Files	Coverage Δ
lib/util/deprecated-apis.js	100% <100%> (ø)	⬆️

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[mysticatea]

Sounds good to me. Thank you!