Remove some broken old-style virtual code

Fixes a crash reported on IRC
dbapi/vartree.py: whitespace cleanup
writeable_check.py: Fix RO check (bug 505428)

Use /proc/self/mountinfo which only contains the relevant chroot mounts.
Mountinfo changes are thanks to jcallen for the valuable info he provided.
TaskSequence.py: Fix queue starting (bug 506186)

start_next_task() was making sure there was actually a task to start.
Sort repoman check results in output

Currently, the check results are output in dict order which is
implementation-defined. This makes it hard to compare results coming
from two machines (Python versions).

Instead, sort all the results lexically.
emerge: call setlocale() to enable system locale

This is necessary so that the size formatting function (and possibly
other locale-dependant functions in the future) respect the system
locale rather than using the 'C' locale.
Use a localized size formatting function

A similar size formatting function was used in two places in emerge
code. Instead, create a single function in portage.localization module
that formats sizes using the current locale and a common set of rules.

I'm not really convinced about 'ceiling' all sizes but I understand
the original point about not outputting '0 KiB'. If you have better
ideas, I'd be happy to change it.

The code was simplified, and a proper number formatting function
is used (instead of string splitting). Locale grouping rules are
respected now, and ISO/IEC binary prefixes are used for unambiguity.
repoman: Remove obsolete eclass checks
DEVELOPING: 50 char limit for summary is too short

Upping it to 70, so with a file/module name prefix and
a bug postfix, there should be some space left for something intelligible.