fb: reexport fbGetGCPrivateKey and add itw wrapped version

This patch reexports a symbol needed by NVidia 340 driver and adds
its "wrapped" version for libwfb to prevent XServer crashes.

Signed-off-by: Oleh Nykyforchyn <oleh.nyk@gmail.com>

fb/fb.h

@@ -254,8 +254,8 @@ fbGetScreenPrivateKey(void);
 /* private field of a screen */
 typedef struct {
 #ifdef FB_ACCESS_WRAPPER
-    SetupWrapProcPtr setupWrap; /* driver hook to set pixmap access wrapping */
-    FinishWrapProcPtr finishWrap;       /* driver hook to clean up pixmap access wrapping */
+    SetupWrapProcPtr setupWrap;   /* driver hook to set pixmap access wrapping */
+    FinishWrapProcPtr finishWrap; /* driver hook to clean up pixmap access wrapping */
 #endif
     DevPrivateKeyRec    gcPrivateKeyRec;
     DevPrivateKeyRec    winPrivateKeyRec;

fb/fb_priv.h

@@ -12,7 +12,10 @@
 
 #define FbBitsStrideToStipStride(s) (((s) << (FB_SHIFT - FB_STIP_SHIFT)))
 
-#define fbGetGCPrivateKey(pGC) (&fbGetScreenPrivate((pGC)->pScreen)->gcPrivateKeyRec)
+/* NVidia v.340 legacy driver needs this symbol */
+extern _X_EXPORT DevPrivateKey
+fbGetGCPrivateKey(GCPtr pGC);
+
 #define fbGetGCPrivate(pGC) ((FbGCPrivPtr)dixLookupPrivate(&(pGC)->devPrivates, fbGetGCPrivateKey(pGC)))
 
 #define fbGetScreenPixmap(s)    ((PixmapPtr) (s)->devPrivate)

fb/fballpriv.c

@@ -25,12 +25,19 @@
 #include "fb/fb_priv.h"
 
 static DevPrivateKeyRec fbScreenPrivateKeyRec;
+
 DevPrivateKey
 fbGetScreenPrivateKey(void)
 {
     return &fbScreenPrivateKeyRec;
 }
 
+DevPrivateKey
+fbGetGCPrivateKey(GCPtr pGC)
+{
+    return &fbGetScreenPrivate((pGC)->pScreen)->gcPrivateKeyRec;
+}
+
 Bool
 fbAllocatePrivates(ScreenPtr pScreen)
 {

fb/wfbrename.h

@@ -55,6 +55,7 @@
 #define fbGCFuncs wfbGCFuncs
 #define fbGCOps wfbGCOps
 #define fbGeneration wfbGeneration
+#define fbGetGCPrivateKey wfbGetGCPrivateKey
 #define fbGetImage wfbGetImage
 #define fbGetScreenPrivateKey wfbGetScreenPrivateKey
 #define fbGetSpans wfbGetSpans