Reserve capacity when decoding HPACK headers (#118)
Reserve capacity when decoding HPACK headers (#118)

Motivation:

I was seeing frequent reallocations of the headers array as it
resized during decoding.

Modifications:

Reserve capacity for at least 16 HPACK headers during decoding.

Result:

Fewer reallocations at the cost of allocating more than we might need.
apple/swift-nio-http2,apple/swift-nio-http2,apple/swift-nio-http2,apple/swift-nio-http2