set Acquire::PDiffs::FileLimit to 20 to avoid needless huge fetches
add new "apt-get upgrade --with-allow-new" option

The --with-allow-new option maps to APT::Get::UpgradeAllowNew and
will allow "apt-get upgrade" to install new packages (but not to
delete existing packages)
add man-page, improve option, use --with-new-pkgs as the flag
its --with-new-pkgs
Merge remote-tracking branch 'upstream/debian/sid' into feature/upgrade-with-new
implement StringSplit() as we need this to fix the dpkg status-fd output parsing
add maxsplit parameter to StringSplit
fix multiarch status-fd progress calculation
doc update
improve the API for Upgrade()
rename "--dpkg-progress" to "--show-progress" and document it in apt-get.8
improve documentation for StringSplit()
change maxsplit default from "0" to maxint
make dpkg progress slightly nicer
Merge remote-tracking branch 'origin/bugfix/dpkg-progress-multiarch' into bugfix/dpkg-progress-multiarch
Merge remote-tracking branch 'mvo/bugfix/dpkg-progress-multiarch' into debian/sid
Merge remote-tracking branch 'donkult/debian/sid' into debian/sid
cleanup upgrade API some more (thanks for the feedback from David)
re-add "Calculating upgrade..." message
* move upgrade releated code into upgrade.{cc,h}

The upgrade releated code is moved into upgrade.{cc,h} and
all pkg*Upgrade* prototypes are included in algorihms.h to
avoid breaking API (unless build with APT_9_CLEANER_HEADERS).