Moved a bunch of definitions from gdi.h into a new gdi_private.h to
make sure we don't use them outside of gdi32.

diff --git a/objects/gdiobj.c b/objects/gdiobj.c
index 7d3add3..d66afa0 100644
--- a/objects/gdiobj.c
+++ b/objects/gdiobj.c
@@ -35,12 +35,15 @@
 #include "local.h"
 #include "palette.h"
 #include "gdi.h"
+#include "gdi_private.h"
 #include "wine/debug.h"
 
 WINE_DEFAULT_DEBUG_CHANNEL(gdi);
 
 #define HGDIOBJ_32(h16)   ((HGDIOBJ)(ULONG_PTR)(h16))
 
+#define GDI_HEAP_SIZE 0xffe0
+
 /***********************************************************************
  *          GDI stock objects
  */