Merged from trunk 6209:6217

Merged from trunk 6209:6217

Automatically convert ROOT and PORTAGE_CONFIGROOT to absolute paths when
necessary since relative paths lead to problems.  Thanks to Christian
Heim <phreak@gentoo.org> for reporting.

Add back rstrip(os.path.sep) from the previous commit since it's needed
when ROOT="/".

For bug #163262 and conformance with section 7.2 of the PMS, make the
export attribute of variables persist between ebuild phases.

For bug #171117, ensure that the new and old config have different
timestamps (for the benefit of programs like rsync that need
distiguishable timestamps to detect file changes).  Thanks to Ben
Bennett <sink@limey.net> for reporting.

Fix a utime call to prevent a timestamp collision for bug #171117.

svn path=/main/branches/prefix/; revision=6235