Substitute dependencies?

[Robert Huff]

Eitan Adler writes:

>  >  Another case I think of is mysql as a dependency when the user
>  >  might prefer MariaDB or PostgreSQL. 
>
>  This may not always be possible, but I do understand the point
>  you are trying to make

	Having never experimented with this, it is my understanding
there are some cases where such substitution is possible, but many
more where it is not.  One would hope if it were, it would be taken
care of in the Makefile or OPTIONS.
	If you know of cases where it _can_ be done (i.e. you have done
it successfully), please (at the very least) post them.  If you're
feeling really motivated, patches would be as welcome to others as
they would have been yo you.

	Respectfully,


				Robert Huff