Update dex file magic number.

Even though the dex format was technically resilient with respect to
the addition of new opcodes, consensus is that the errors one sees
when trying to use a new dex file on an old build were sufficiently
inscrutable that it was worth the effort to update the version number
embedded in the dex format magic.

This change updates dx to produce the new version number when extended
opcodes are enabled (which is the default, but may be overridden by
targeting an older API level).

This also updates the vm to recognize and accept both the new current
version number as well as the immediately previous one. Note: It won't
reject an old-version file if it happens to use the new opcodes; that
would just be a gratuitous and pointless failure.

Bug: 4364986
Change-Id: If8febbb0b91c1719df4247bf69c511251362d91f
12 files changed