Reorganize logging

- Move the opening/closing of logs to the log package
- Use conditional compilation for redirecting stdout/err to logfile,
  Unix allows a superior method to Windows
- Panic output will now to go log file on Unix platforms

log/stdout_windows.go

@@ -0,0 +1,37 @@
+// +build windows
+
+package log
+
+import (
+	"os"
+)
+
+var stdOutsClosed = false
+
+// closeStdin does nothing on Windows, it would always fail
+func closeStdin() {
+	// Nop
+}
+
+// reassignStdout points stdout/stderr to our logfile on systems that do not
+// support the Dup2 syscall
+func reassignStdout() {
+	Tracef("Windows reassignStdout()")
+	if !stdOutsClosed {
+		// Close std* streams to prevent accidental output, they will be redirected to
+		// our logfile below
+
+		// Warning: this will hide panic() output, sorry Windows users
+		if err := os.Stderr.Close(); err != nil {
+			// Not considered fatal
+			Errorf("Failed to close os.Stderr during log setup")
+		}
+		if err := os.Stdin.Close(); err != nil {
+			// Not considered fatal
+			Errorf("Failed to close os.Stdin during log setup")
+		}
+		os.Stdout = logf
+		os.Stderr = logf
+		stdOutsClosed = true
+	}
+}