UI: Add pause support

Adds support for pausing recordings.  When settings are eligible for
recordings, a pause button will appear next to the recording button.  If
the settings are not eligible, it will warn the user in the output
settings that they cannot pause recordings if those settings are used.

UI/window-basic-status-bar.cpp

@@ -241,17 +241,28 @@ void OBSBasicStatusBar::UpdateStreamTime()
 	}
 }
 
+extern volatile bool recording_paused;
+
 void OBSBasicStatusBar::UpdateRecordTime()
 {
-	totalRecordSeconds++;
+	bool paused = os_atomic_load_bool(&recording_paused);
 
-	int seconds = totalRecordSeconds % 60;
-	int totalMinutes = totalRecordSeconds / 60;
-	int minutes = totalMinutes % 60;
-	int hours = totalMinutes / 60;
+	if (!paused)
+		totalRecordSeconds++;
 
 	QString text;
-	text.sprintf("REC: %02d:%02d:%02d", hours, minutes, seconds);
+
+	if (paused) {
+		text = QStringLiteral("REC: PAUSED");
+	} else {
+		int seconds = totalRecordSeconds % 60;
+		int totalMinutes = totalRecordSeconds / 60;
+		int minutes = totalMinutes % 60;
+		int hours = totalMinutes / 60;
+
+		text.sprintf("REC: %02d:%02d:%02d", hours, minutes, seconds);
+	}
+
 	recordTime->setText(text);
 	recordTime->setMinimumWidth(recordTime->width());
 }