package.bbclass: Add additional debugging for dependencies

package.bbclass: Add additional debugging for dependencies

When trying to understand why a QA wanring such as:

ERROR: QA Issue: foo rdepends on bar-dev

it is very difficult to figure out where the bar-dev dependency
comes from, since many of them are added dynamically.

This adds a debug statement that says which dependency adds an
rdepends to the system.

Also, while doing this work, it was noted that the same dependencies
were being scanned for over and over.  Instead we shorten the list
by only added to the dep list if the dependency was not already there.

(From OE-Core rev: 257b9e371143421b78a6991ef5401e564918c164)

Signed-off-by: Mark Hatle <mark.hatle@windriver.com>
Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>