Userland: Move HOST_NAME_MAX to limits.h

POSIX mandates its definition there.

Userland/Libraries/LibC/limits.h

@@ -12,6 +12,8 @@
 #    define PAGE_SIZE 4096
 #endif
 
+#define HOST_NAME_MAX 64
+
 #define PATH_MAX 4096
 #if !defined MAXPATHLEN && defined PATH_MAX
 #    define MAXPATHLEN PATH_MAX

Userland/Libraries/LibC/unistd.h

@@ -129,8 +129,6 @@ enum {
     _PC_VDISABLE
 };
 
-#define HOST_NAME_MAX 64
-
 #define R_OK 4
 #define W_OK 2
 #define X_OK 1

Userland/Utilities/hostname.cpp

@@ -6,6 +6,7 @@
 
 #include <LibCore/ArgsParser.h>
 #include <errno.h>
+#include <limits.h>
 #include <stdio.h>
 #include <string.h>
 #include <unistd.h>

Userland/Utilities/tree.cpp

@@ -12,6 +12,7 @@
 #include <LibCore/ArgsParser.h>
 #include <LibCore/DirIterator.h>
 #include <errno.h>
+#include <limits.h>
 #include <stdio.h>
 #include <sys/stat.h>
 #include <unistd.h>