Mac OS X fixes: include string.h, add strndup(), disable xmllint for the docs

i3bar/doc/Makefile

@@ -2,7 +2,7 @@ all: i3bar.1
 
 i3bar.1: i3bar.man
 	echo "A2X i3bar"
-	a2x -f manpage i3bar.man
+	a2x --no-xmllint -f manpage i3bar.man
 clean:
 	rm -f i3bar.xml i3bar.1 i3bar.html
 

i3bar/src/ipc.c

@@ -12,6 +12,7 @@
 #include <stdio.h>
 #include <unistd.h>
 #include <stdint.h>
+#include <string.h>
 #include <errno.h>
 #include <sys/socket.h>
 #include <sys/un.h>

i3bar/src/xcb.c

@@ -27,6 +27,30 @@
 
 #include "common.h"
 
+#if defined(__APPLE__)
+
+/*
+ * Taken from FreeBSD
+ * Returns a pointer to a new string which is a duplicate of the
+ * string, but only copies at most n characters.
+ *
+ */
+char *strndup(const char *str, size_t n) {
+    size_t len;
+    char *copy;
+
+    for (len = 0; len < n && str[len]; len++)
+        continue;
+
+    if ((copy = malloc(len + 1)) == NULL)
+        return (NULL);
+    memcpy(copy, str, len);
+    copy[len] = '\0';
+    return (copy);
+}
+
+#endif
+
 /* We save the Atoms in an easy to access array, indexed by an enum */
 enum {
     #define ATOM_DO(name) name,