let BUILDFIRST just build first, using the same trick guenther@ did in

let BUILDFIRST just build first, using the same trick guenther@ did in
kernel Makefiles (thank you!), also add lex and yacc generated files to
that list.

Let those lex/yacc variables be defined for bsd.lib.mk as well.

Complete the SRCS -> OBJS hints with the library dependency

This should fix most dependency problems.

Commit now, so that people can check if something else is still amiss.
krw@ agrees