InfoBoxes/Panel/MacCreadyEdit: Fix MC adjustment for non metric settings

Fixes trac issue #2654.
InterfaceConfigPanel: fix require_restart setters

The expression "require_restart |= changed |= X" always sets
"require_restart" to true if "changed" was set by another control.
This causes false positives in "require_restart".
{GC,Layout}ConfigPanel: fix require_restart setters

Similar to the previous commit.  The code was not exactly wrong, but
was misleading the (human) reader.
Makefile: enable TESTING

This is the unstable branch.
NEWS.txt: prepare version 6.5.1
IO/FileCache: move code to FileTimeToInteger()
FileCache: use the cache even when the system clock is wrong

Replaces an old kludge that was Windows CE only.  This can happen on
Android devices, too.
NEWS.txt: add missing lines
WinInet/Request: consistently restore the StatusCallback

Convert the URL to wchar_t before invoking SetStatusCallback().
Errors during the former will not corrupt the callback.
NMEA/Info: remove deprecated prototype ResetFlight()

Not implemented.
Replay: fix the Update() return value

Return true if the AbstractReplay instance has been updated
successfully.  Fixes auto-stop on GPS movement and suppresses the
simulator while replay is active.
Merge branch 'v6.5.x'
Replay: simplify Update()
Time/PeriodClock: rename get_now() to GetNow()
Time/PeriodClock: add overloads with Stamp parameter

For reducing the number of GetNow() calls in combined methods.
Time/PeriodClock: add method ElapsedUpdate()
Replay: skip Update() if replay is paused
Replay/CatmullRomInterpolator: add header guards
Replay: move time-keeping code from AbstractReplay to Replay

Prepare for merging with the DebugReplay library and for a
"fast-forward" button.
ConditionMonitorSunset: check date_available()

Fixes potential assertion failure.