Move back the XChar2b definition to w32gui.h and nsgui.h

Fix the last change.  XChar2b still needs to be defined platform dependently,
to match with the argument types of drawing functions.

src/ChangeLog

@@ -3,10 +3,10 @@
 	Consolidate XChar2b macros for the X, W32, and NS
 	Suggested by Jan Djärv in:
 	https://lists.gnu.org/archive/html/emacs-devel/2014-07/msg00203.html
-	* w32gui.h (XChar2b, STORE_XCHAR2B, XCHAR2B_BYTE1, XCHAR2B_BYTE2):
-	Move the fallback definitions to dispextern.h.
-	* nsgui.h (XChar2b, STORE_XCHAR2B, XCHAR2B_BYTE1, XCHAR2B_BYTE2):
-	Likewise.  Share the same definition with W32.
+	* w32gui.h (STORE_XCHAR2B, XCHAR2B_BYTE1, XCHAR2B_BYTE2): Move the
+	fallback definitions to dispextern.h.
+	* nsgui.h (STORE_XCHAR2B, XCHAR2B_BYTE1, XCHAR2B_BYTE2): Likewise.
+	Share the same definition with W32.
 	* xterm.h (STORE_XCHAR2B, XCHAR2B_BYTE1, XCHAR2B_BYTE2): Move to ...
 	* dispextern.h (STORE_XCHAR2B, XCHAR2B_BYTE1, XCHAR2B_BYTE2):
 	... here for the consistency with W32 and NS.

src/dispextern.h

@@ -51,8 +51,6 @@ typedef struct {
   char pad;
 } XColor;
 
-typedef unsigned short XChar2b;
-
 #define STORE_XCHAR2B(chp, b1, b2) \
   (*(chp) = ((XChar2b)((((b1) & 0x00ff) << 8) | ((b2) & 0x00ff))))
 

src/nsgui.h

@@ -58,6 +58,14 @@ typedef struct _XCharStruct
   int descent;
 } XCharStruct;
 
+/* Fake structure from Xlib.h to represent two-byte characters.  */
+#ifdef HAVE_NS
+#ifndef __OBJC__
+typedef unsigned short unichar;
+#endif
+typedef unichar XChar2b;
+#endif
+
 
 /* XXX: xfaces requires these structures, but the question is are we
         forced to use them? */

src/w32gui.h

@@ -52,6 +52,8 @@ typedef HCURSOR Cursor;
 
 #define No_Cursor (0)
 
+#define XChar2b wchar_t
+
 
 /* Windows equivalent of XImage.  */
 typedef struct _XImage