selectively importFrom parallel, to avoid clobbering local defs
add AGGREGATE argument to bpvec

- don't check, in local pvec, for 'length' mismatch, since
  return value might not have an appropriate length (e.g., data.frame)
use BPPARAM rather than param for argument name

- better name mangling to avoid conflicts with 'param's of other functions
bplapply, bpvec dispath only on X, BPPARAM

- avoid complicated 4-argument dispatch possibilities
documentation clean-up

- document AGGREGATE argument of bpvec
- document register, registered functions
- typos, etc
version bump
condition import from parallel

- windows compatibility
man page example typos
make unit tests OS-dependent

- catch 'fork clusters are not supported on Windows' err
windows isChild alias required
avoid man page link to parallel::mcparallel

- no Windows documentation available