I am planning to push the bufmgr.c patch soon. At that point the new
API won't have any direct callers yet, but the traditional
ReadBuffer() family of functions will internally reach
StartReadBuffers(nblocks=1) followed by WaitReadBuffers(),
ZeroBuffer() or nothing as appropriate. Any more thoughts or
objections? Naming, semantics, correctness of buffer protocol,
sufficiency of comments, something else?