Added header guards; fixed linter errors

src/arg.h

@@ -3,8 +3,8 @@
  * by 20h
  */
 
-#ifndef ARG_H__
-#define ARG_H__
+#ifndef ARG_H
+#define ARG_H
 
 extern char *argv0;
 

src/st/st.h

@@ -1,7 +1,11 @@
 /* See LICENSE for license details. */
 
+#ifndef ST_H
+#define ST_H
+
 #include <stdint.h>
 #include <sys/types.h>
+#include <stddef.h>
 
 /* macros */
 #define MIN(a, b)		((a) < (b) ? (a) : (b))
@@ -123,3 +127,5 @@ extern char *termname;
 extern unsigned int tabspaces;
 extern unsigned int defaultfg;
 extern unsigned int defaultbg;
+
+#endif

src/win.h

@@ -1,5 +1,10 @@
 /* See LICENSE for license details. */
 
+#ifndef WIN_H
+#define WIN_H
+
+#include "st/st.h"
+
 enum win_mode {
 	MODE_VISIBLE     = 1 << 0,
 	MODE_FOCUSED     = 1 << 1,
@@ -38,3 +43,5 @@ void xsetpointermotion(int);
 void xsetsel(char *);
 int xstartdraw(void);
 void xximspot(int, int);
+
+#endif