Make visible symbols required by xorg modules.

This patch exports all symbols required by the compilable
(in a x86 linux computer) xorg/driver/* modules.
  Still missing symbols worth mentioning are:

sunleo
	miFindMaxBand no longer available

intel	(uxa/uxa-accel.c)
	fbShmPutImage no longer available (and should have been static)

mga
	MGAGetClientPointer (should come from matrox's libhal)

  This is not a definitive "visibility" patch, as all it does is to
export missing symbols, but the modules that current don't compile,
may require more symbols once fixed, and third party drivers should
also require more symbols exported.
  A "definitive" patch should export symbols defined in the sdk.

hw/xfree86/vbe/vbe.c

@@ -41,7 +41,7 @@ static Bool vbeProbeDDC(vbeInfoPtr pVbe);
 
 static const char vbeVersionString[] = "VBE2";
 
-vbeInfoPtr
+_X_EXPORT vbeInfoPtr
 VBEInit(xf86Int10InfoPtr pInt, int entityIndex)
 {
     return VBEExtendedInit(pInt, entityIndex, 0);
@@ -423,7 +423,7 @@ VBEGetVBEInfo(vbeInfoPtr pVbe)
     return (block);
 }
 
-void
+_X_EXPORT void
 VBEFreeVBEInfo(VbeInfoBlock *block)
 {
     xfree(block->OEMStringPtr);
@@ -501,7 +501,7 @@ VBEGetVBEMode(vbeInfoPtr pVbe, int *mode)
     return (FALSE);
 }
 
-VbeModeInfoBlock *
+_X_EXPORT VbeModeInfoBlock *
 VBEGetModeInfo(vbeInfoPtr pVbe, int mode)
 {
     VbeModeInfoBlock *block = NULL;
@@ -596,7 +596,7 @@ VBEGetModeInfo(vbeInfoPtr pVbe, int mode)
     return (block);
 }
 
-void
+_X_EXPORT void
 VBEFreeModeInfo(VbeModeInfoBlock *block)
 {
     xfree(block);