webkit: Change detection of which devices can use V8 and whether non vfp devices can use LARGE_MEMORY flag

This commit allows ARMv6 devices to use V8 either because they have VFP or because they have explicitly enabled it through the TARGET_WEBKIT_USE_MO

This patch is based heavily on http://review.cyanogenmod.com/#change,12128 and http://review.cyanogenmod.com/#change,11365

This patch is also dependent on http://review.cyanogenmod.com/#change,12129 - ARMv6 devices crash without it while using V8

Change-Id: I249bb9092e5ad85a25a57c71f2dd4a7d9d430c6c