for a request with an alignment requirement, uvm_map_findspace
tries aligned addresses first and then siliently fall back to
non-aligned addresses.
it might be bad for callers assuming returned addresses are
properly aligned.  (e.g. libpthread.)

is there anything relying on this "fallback" behaviour?
i'd like to change it.
i.e. if alignment is specified, try aligned addresses only.

YAMAMOTO Takashi