lep: request all the things

POSIX requires that it has a range of at least -1 to 32,767 but in practice it's a signed int or long.  I suppose an int is alright; it's consistent with uv_try_write() and 2^31-1 is still pretty big.

Apropos signed vs. unsigned, nbufs should probably be unsigned; its uv_try_write() counterpart is.  (And bufs is const.)