Kernel/LibC: implement chmod syscall + libc wrapper

libc/include/sys/syscall.h

@@ -55,6 +55,7 @@ __BEGIN_DECLS
 #define SYS_MUNMAP 52
 #define SYS_TTY_CTRL 53
 #define SYS_POWEROFF 54
+#define SYS_CHMOD 55
 
 __END_DECLS
 

libc/sys/stat.cpp

@@ -4,6 +4,11 @@
 #include <sys/syscall.h>
 #include <unistd.h>
 
+int chmod(const char* path, mode_t mode)
+{
+	return syscall(SYS_CHMOD, path, mode);
+}
+
 int fstat(int fildes, struct stat* buf)
 {
 	return syscall(SYS_FSTAT, fildes, buf);