swift234

stdlib: Factor _copy*ToNativeArrayBuffer into a general-purpose "builder" for ContiguousArrayBuffer.

This makes the code for efficiently initializing array buffers in-place more accessible to the rest of the standard library, and should also provide a performance boost for _copySequenceToNativeArrayBuffer, which had been implemented as a naive append loop, by handling reallocating the buffer when necessary when initializing from a sequence that underestimates its count.

Swift SVN r30793