Screen/Windows: Allow disable of processor idling disable.

We want a way out of the new C-state switching prevention code on Windows.
Now check for existence environment variable PSYCH_DONT_DISABLE_CPU_IDLING
and don't disable processor idling / C-state switching if the variable is set.

The new PsychTweak('DontDisableProcessorIdling', dontDisable) setting
allows to control this from user scripts.

Note this commit also changes end of line markers from DOS CR+LF to Unix
LF, hence the potential impression of large scale changes in this file
with some commit diff tools.

PsychSourceGL/Source/Windows/Screen/PsychWindowGlue.c

@@ -367,6 +367,11 @@ psych_bool PsychOSDisableProcessorIdling(psych_bool dontIdle)
 {
     GUID* activeScheme;
 
+    // No-Op with success return if env variable PSYCH_DONT_DISABLE_CPU_IDLING is defined,
+    // for testing or for interop with cpu tweaking tools - settable via PsychTweak():
+    if (getenv("PSYCH_DONT_DISABLE_CPU_IDLING"))
+        return(TRUE);
+
     if (PowerGetActiveScheme(NULL, &activeScheme) ||
         PowerWriteACValueIndex(NULL, activeScheme, &GUID_PROCESSOR_SETTINGS_SUBGROUP, &GUID_PROCESSOR_IDLE_DISABLE, dontIdle ? 1 : 0) ||
         PowerWriteDCValueIndex(NULL, activeScheme, &GUID_PROCESSOR_SETTINGS_SUBGROUP, &GUID_PROCESSOR_IDLE_DISABLE, dontIdle ? 1 : 0) ||