vendor/bmake: upgrade from 20160818 to 20200710

vendor/bmake: upgrade from 20160818 to 20200710

Summary of notable changes:

- add :range and :_
- support for .DELETE_ON_ERROR
- allow specifying the utc value used by :{gm,local}time
- allow :_=var and avoid use of special context
- use -C arg "as is" if it contains no relative component
- when setting .OBJDIR, ignore '$' in paths
- add -v option to always fully expand values
- pass SIGINT etc onto child and wait for it to exit
- when target is out-of-date per normal make rules record
  value of .OODATE in meta file
- add :Or for reverse sort
- improvements to avoid unnecessary evaluation use enums
  for flags
- debugging output for :@
- fix for compare_expression when doEval=0

For detailed list see ChangeLog.