* utils/hbmk2/hbmk2.prg
+ -autohbc now has natural defaults, header part will
automatically get .ch extension, .hbc part will automatically
get .hbc extension. If .hbc is not specified, it will become
the same as header name. So f.e. '-autohbc=hbwin.ch:hbwin.hbc'
can be written simply as: '-autohbx=hbwin'.