cleanup

Change-Id: I14f07a52f6a4093001b863c4b40ca9696b37a05d
[flow] vm: Implements regex-match plus some related cleanups.

Change-Id: I424c9d5bb6c4008128d5c1affb3c294302ea2f24
[flow] sema: implements strict type checking on variable assignment.

A variable must not change type after initialization.

Change-Id: I18cca3707a1f59ae1b60fab21272f7f19977e1ee
update

Change-Id: Id9eaea247209ba4c220a8a5b94f12566b2d68f6f
[flow] vm: work towards regex match context

Change-Id: I5e2fedbf39d2a7991b5a8962567258fb17478d8d
update

Change-Id: I3797a89133f1b9e201caa5ae346cbc826d468ec2
[flow] vm: fixes crash on regex-match with no contextual userdata set.

Change-Id: I2b05e8e39bc3a8ec413932ab3cd235ecc72a037f