PsychHID/OSX: Fix conversion of HID event timestamps to GetSecs time.

Timestamps delivered by the HID subsystem are in mach time units, arbitrary units for a given
machines clock hardware. On Intel based Macs, the units happened to be fixed across all machines
to be Nanoseconds, so a simple division by 1e9 did the conversion. On Apple Silicon ARM Macs, the
units are no longer Nanoseconds, but something odd - probably something like bus frequency or
whatever. Therefore we need to use a proper adaptive conversion, which is querying the mach
timebase frequency, via PsychGetKernelTimebaseFrequencyHz() and then dividing by that.

This provides proper conversion and fixes the input event timestamps of keyboard queues -
KbQueueDemo now prints proper keypress times.

When we are at it, make PsychGetKernelTimebaseFrequencyHz() a tad more efficient.

PsychSourceGL/Source/OSX/Base/PsychTimeGlue.c

@@ -106,11 +106,11 @@ double PsychYieldIntervalSeconds(double delaySecs)
 
 double PsychGetKernelTimebaseFrequencyHz(void)
 {
-    long double                 clockPeriodNSecs;
-    mach_timebase_info_data_t   tbinfo;
+    if (!isKernelTimebaseFrequencyHzInitialized) {
+        long double                 clockPeriodNSecs;
+        mach_timebase_info_data_t   tbinfo;
 
-    if(!isKernelTimebaseFrequencyHzInitialized){
-        // Retrieve the mach absolute time timebase.  The kernel expresses the period in two integers, the ratio of which is the clock period.
+        // Retrieve the mach absolute time timebase. The kernel expresses the period in two integers, the ratio of which is the clock period.
         mach_timebase_info(&tbinfo);
 
         // Calculate the mach timebase period from values reported from the mach kernel.
@@ -120,10 +120,10 @@ double PsychGetKernelTimebaseFrequencyHz(void)
         // Frequency in Hz is a convenient form because it makes converting from a period in seconds into a period in mach timebase units easy:
         //  time_interval_in_mach_units= time_interval_in_seconds * clockFrequencyHz;
         kernelTimebaseFrequencyHz = 1000000000.0 / clockPeriodNSecs;
-        isKernelTimebaseFrequencyHzInitialized=TRUE;
+        isKernelTimebaseFrequencyHzInitialized = TRUE;
     }
 
-    return((double)kernelTimebaseFrequencyHz);
+    return((double) kernelTimebaseFrequencyHz);
 }
 
 /* Called at Module init time: */

PsychSourceGL/Source/OSX/PsychHID/PsychHIDStandardInterfaces.c

@@ -729,7 +729,7 @@ enum { kHID2VKCSize = sizeof kHID2VKC / sizeof kHID2VKC[0] };
 // Convert uint64 time in nanoseconds to double value in GetSecs() seconds:
 static double convertTime(uint64_t timeUInt64) {
     double timeDouble = (double) timeUInt64;
-    return timeDouble / 1000000000;
+    return timeDouble / PsychGetKernelTimebaseFrequencyHz();
 }
 
 static void PsychHIDKbQueueCallbackFunction(void *target, IOReturn result, void *sender)