wined3d: Don't create more than WINED3D_MAX_FBO_ENTRIES FBO entries.

This essentially turns the FBO entry list into an LRU cache.
diff --git a/dlls/wined3d/wined3d_private.h b/dlls/wined3d/wined3d_private.h
index c227e9c..cbefa9a 100644
--- a/dlls/wined3d/wined3d_private.h
+++ b/dlls/wined3d/wined3d_private.h
@@ -1167,6 +1167,8 @@
     FOGSOURCE_COORD,
 };
 
+#define WINED3D_MAX_FBO_ENTRIES 64
+
 /* The new context manager that should deal with onscreen and offscreen rendering */
 struct WineD3DContext {
     /* State dirtification
@@ -1214,6 +1216,7 @@
     GLint                   aux_buffers;
 
     /* FBOs */
+    UINT                    fbo_entry_count;
     struct list             fbo_list;
     struct fbo_entry        *current_fbo;
     GLuint                  src_fbo;