Copy head (r256279) to stable/10 as part of the 10.0-RELEASE cycle.Approved by: re (implicit)Sponsored by: The FreeBSD Foundation
Add a missing space to the error message when execvp() failed.
Factor out ProcExec() into its own file and rename it to Proc_Exec() forconsistency with the rest of make.Obtained from: DragonFlyBSD (except for the rename)