fix browser-xhr bundling for es5 lib

[pelle]

When adding ipfs-mini to a web pack like build process for a browser it can't find the xml http request object.

It's a pretty simple fix that just needs a mapping from the lib version to the browser lib version.

ipfs-mini

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[coveralls]

Coverage remained the same at 100.0% when pulling 2c2522ff2e196d7341c55ad0d054d629204ffd02 on pelle:fix-es5-xhr into 9f3c2e16a9430fcdcc19e107f2b0c284ef1e0dac on SilentCicero:master.