squash! Validate that OML Sync Control syncs to vblank.

v3: Per Chris Wilson, don't require a glXGetSyncValuesOML call
immediately after glXWaitForSbc/Msc to return the same UST or MSC,
because uncontrolled delays during the test may mean that the counters
increment between the two calls. Instead, require that alternating
GetSyncValues and Wait calls return monotonically increasing UST and MSC
values. Since a common failure mode in the current drivers is to return
UST and MSC as 0 from the WaitForSbc/Msc requests (which obviously
violates monotonicity), if those values are illegal, try to muddle
through the rest of the test using the GetSyncValues results instead.
fixup! Validate that OML Sync Control syncs to vblank.

Restore wallclock timing test, which got broken when we wrapped to 80 columns.