better param checking?

[Sven K�hler]

hi!

is there a way to tell configure to check params like --with-foo?

./configure --foo failes with an error
./configure --with-foo doesn't fail ... it just ignores the "--with-foo" option.

this might also apply to --enable-foo

./configure --with-foo should fail with the message, that the option called "foo" is not available.

any hints?