Tablet workaround for RecentApplicationsDialog

At least on Nook Color and ZTE V9/Light which both are WVGA + MDPI devices there is a bug with
the recent applications dialog. This patch provides a workaround for the problem and it is
activated by setting "cm_default_recentapps_tablet_workaround" to true in config.xml.

I choose to quote a user in the CyanogenMod Nook Color forum that desribed the bug like this:
"I have problems with this on my Nook sometimes. When it works, I get the recent apps centered
upon a vertical transparent-black-transparent gradient. Otherwise, it's a small black box of
recent apps, aligned to the upper border and centered horizontally."

Here's post at the Modaco forum with a screenshot that shows what it looks like when it goes bad:
http://android.modaco.com/topic/340064-romgingerbreadcm7-working-on-gen2-zte-lightv9-2011-08-15/page__st__440__p__1784691#entry1784691

It appears that sometimes (seemingly random) the recent apps choose HVGA dimensions on WVGA/MDPI
tablets. Also the lockscreen does this on the first boot after a wipe but after the first reboot
it never happens again so that's not even worth trying to fix. But the recent applications dialog
keep doing this perhaps 50% of the times you bring it up so it needs to be fixed.

The reason why I made this workaround optional is that it has one issue. If you change the
orientation of the device when the recent applications dialog is shown it will not resize itself
correctly unless you close it and bring it up again.

Now if anyone has a better fix or workaround then I'm open for suggestions.

Change-Id: I505fac85d355dc8c42410863da3081b56fa71891