Restore power management for OS X < 10.9.

This code is based on the implementation used in earlier versions of FileZilla.

--- ./src/interface/power_management.cpp.orig	2020-06-18 16:06:46.000000000 +0200
+++ ./src/interface/power_management.cpp	2023-03-25 20:41:35.000000000 +0100
@@ -112,7 +112,7 @@
 #ifdef __WXMSW__
 	return true;
 #endif
-#if defined(__WXMAC__)
+#if defined(__WXMAC__) && MAC_OS_X_VERSION_MAX_ALLOWED >= 1050
 	return true;
 #endif
 #ifdef WITH_LIBDBUS
--- ./src/interface/power_management_osx.mm.orig	2020-06-04 12:18:02.000000000 +0200
+++ ./src/interface/power_management_osx.mm	2023-03-25 20:43:11.000000000 +0100
@@ -1,18 +1,48 @@
+#include <AvailabilityMacros.h>
+
+#if MAC_OS_X_VERSION_MAX_ALLOWED >= 1090
 #include <Foundation/NSProcessInfo.h>
+#elif MAC_OS_X_VERSION_MAX_ALLOWED >= 1050
+#include <cstdlib>
+#include <IOKit/pwr_mgt/IOPMLib.h>
+#endif
 
 void const* PowerManagmentImpl_SetBusy()
 {
+#if MAC_OS_X_VERSION_MAX_ALLOWED >= 1090
 	NSActivityOptions opt = NSActivityUserInitiated | NSActivityIdleSystemSleepDisabled;
 	id activity = [[NSProcessInfo processInfo] beginActivityWithOptions:opt reason:@"Preventing idle sleep during transfers and other operations."];
 	return CFBridgingRetain(activity);
+#elif MAC_OS_X_VERSION_MAX_ALLOWED >= 1050
+	IOPMAssertionID assertionID;
+	IOReturn success = IOPMAssertionCreate(kIOPMAssertionTypeNoIdleSleep, kIOPMAssertionLevelOn, &assertionID);
+	if (success == kIOReturnSuccess) {
+		IOPMAssertionID* ret = (IOPMAssertionID*)malloc(sizeof(assertionID));
+		if (ret == NULL) {
+			return 0;
+		}
+		*ret = assertionID;
+		return ret;
+	} else {
+		return 0;
+	}
+#endif
 }
 
 void PowerManagmentImpl_SetIdle(void const* activity)
 {
+#if MAC_OS_X_VERSION_MAX_ALLOWED >= 1090
 	if (activity) {
 		id<NSObject> activityId = CFBridgingRelease(activity);
 		[[NSProcessInfo processInfo] endActivity:activityId];
 	}
+#elif MAC_OS_X_VERSION_MAX_ALLOWED >= 1050
+	if (activity) {
+		IOPMAssertionID assertionID = *(IOPMAssertionID*)activity;
+		IOPMAssertionRelease(assertionID);
+		free((void*)activity);
+	}
+#endif
 }