Split into multiple files

For multiple reasons the program is now split:
- Make future porting to OpenBSD easier
- Assign header includes to individiual functions
- Make future program extensions easier
- Recompile only changed parts

keyboard_indicators.c

@@ -0,0 +1,29 @@
+#include <err.h>
+#include <X11/Xlib.h>
+
+#include "util.h"
+
+const char *
+keyboard_indicators(void)
+{
+	Display *dpy = XOpenDisplay(NULL);
+	XKeyboardState state;
+
+	if (dpy == NULL) {
+		warnx("XOpenDisplay failed");
+		return NULL;
+	}
+	XGetKeyboardControl(dpy, &state);
+	XCloseDisplay(dpy);
+
+	switch (state.led_mask) {
+		case 1:
+			return "c";
+		case 2:
+			return "n";
+		case 3:
+			return "cn";
+		default:
+			return "";
+	}
+}