Update 'HowTo-Cross-Compile.md'

HowTo-Cross-Compile.md

@@ -106,6 +106,7 @@ Copy all compiled executeble and library files into the wine windows/system fold
 ## workaround for some issues
 
 edit the file `gdk/win32/gdkprivate-win32.h` and search around line 300 for the following declaration. The compiler is missing the **extern** statement here.
+
 	300 /* The singleton selection object pointer */
 	301 extern GdkWin32Selection *_win32_selection;