Merged from trunk 4770:4783

Merged from trunk 4770:4783

Allow an empty PROMPT_COMMAND for bug #152157.

For bug #152175, trigger greedy --update behavior when an atom matches a
slot that isn't installed yet.

Apply the fix for bug #152175 to system/world greedy behavior.

In greedy atom handlink, filter binary package for visiblity.

More filtering binary package for visiblity in greedy atom handling.

Add nodes to the fakedb in depgraph.create instead of
depgraph.select_deps.  It used to be in select_deps only for the case of
packages that depend on themselves for bootstrap, but that hack isn't
needed anymore because dep_check  returns all deps now.

Update the docs regarding delay of config.setinst calls for bootstrap
deps on old-style virtuals.

Remove redunant population of the fakedb in depgraph.validate_blockers,
since r4776 makes it unnecessary.

Add news about new-style virtuals being usable for bootstrap deps on
self.

Add package.use to the list of files supported in profiles.

Add news about package.use in profiles and default USE in ebuilds via
+flag in IUSE.

For bug #152157, don't send a redundant escape sequence with
${PROMPT_COMMAND}.

Also check keyword visibility via gvisible.

svn path=/main/branches/prefix/; revision=4784