[Issue 19280] New: Remove unnecessary error checks in core.time.currSystemTick

[d-bugmail at puremagic.com]

https://issues.dlang.org/show_bug.cgi?id=19280

          Issue ID: 19280
           Summary: Remove unnecessary error checks in
                    core.time.currSystemTick
           Product: D
           Version: D2
          Hardware: All
                OS: All
            Status: NEW
          Severity: enhancement
          Priority: P1
         Component: druntime
          Assignee: nobody at puremagic.com
          Reporter: n8sh.secondary at hotmail.com

Microsoft Windows QueryPerformanceCounter doesn't fail on Windows XP or later.
https://msdn.microsoft.com/en-us/library/windows/desktop/ms644904(v=vs.85).aspx

Posix gettimeofday called with a valid timeval address and a null second
parameter doesn't fail.
http://pubs.opengroup.org/onlinepubs/9699919799/functions/gettimeofday.html

Posix clock_gettime called with a valid clock_id and a valid timespec address
is in principle allowed to fail if the number of seconds doesn't fit in time_t,
so even though no known implementation does this it is probably best to retain
the error check at this time.
http://pubs.opengroup.org/onlinepubs/9699919799/functions/clock_getres.html

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