Bug 888658 - Assertions.h fixup for windows. r=jwalden

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extra : rebase_source : 7e7fb741860c2603aa1b838eff7761ddcd50e867
Bug 888658 - Add LZ4 compression to mfbt. r=jwalden,vlad

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extra : rebase_source : e92051145948cd3c1e6f95596563d8c13e231ee3