os.setLastModificationTime*(file: string, t: times.Time) (#7543)

* add proc toFILETIME to winlean
* add proc toWinTime to times
* add proc setFileTime to winlean
* openHandle with write access
* add proc setLastModificationTime to os
* moved epochDiff,rateDiff constants and proc toWinTime
The constants were moved out of the when defined(JS) block so that they
are alsways available in proc toWinTime.
proc toWinTime was moved above the # Deprecated procs comment. Best new
location seemed to be with the toUnix proc.

lib/pure/times.nim

@@ -191,6 +191,7 @@ const
   secondsInHour = 60*60
   secondsInDay = 60*60*24
   minutesInHour = 60
+  rateDiff = 10000000'i64 # 100 nsecs
   # The number of hectonanoseconds between 1601/01/01 (windows epoch)
   # and 1970/01/01 (unix epoch).
   epochDiff = 116444736000000000'i64
@@ -371,6 +372,10 @@ proc toUnix*(t: Time): int64 {.benign, tags: [], raises: [], noSideEffect.} =
   ## Convert ``t`` to a unix timestamp (seconds since ``1970-01-01T00:00:00Z``).
   t.seconds
 
+proc toWinTime*(t: Time): int64 =
+  ## Convert ``t`` to a Windows file time (100-nanosecond intervals since ``1601-01-01T00:00:00Z``).
+  result = t.seconds * rateDiff + epochDiff
+
 proc isLeapYear*(year: int): bool =
   ## Returns true if ``year`` is a leap year.
   year mod 4 == 0 and (year mod 100 != 0 or year mod 400 == 0)
@@ -1713,9 +1718,6 @@ when not defined(JS):
   var
     clocksPerSec {.importc: "CLOCKS_PER_SEC", nodecl.}: int
 
-  const
-    rateDiff = 10000000'i64 # 100 nsecs
-
   proc unixTimeToWinTime*(time: CTime): int64 =
     ## converts a UNIX `Time` (``time_t``) to a Windows file time
     result = int64(time) * rateDiff + epochDiff