No, it's not, good guess though. ;-)

```bash
-bash-3.2$ ls $EBROOTXPROTO/include/X11
ap_keysym.h  HPkeysym.h   keysym.h     Xalloca.h  Xatom.h  XF86keysym.h  Xfuncs.h  Xmd.h      Xos.h    Xpoll.h	 Xprotostr.h  Xw32defs.h  Xwindows.h
DECkeysym.h  keysymdef.h  Sunkeysym.h  Xarch.h	  Xdefs.h  Xfuncproto.h  X.h	   Xosdefs.h  Xos_r.h  Xproto.h  Xthreads.h   XWDFile.h   Xwinsock.h
```