cmdutils: remove the current working directory from the DLL search path on win32

Reviewed-by: Matt Oliver <protogonoi@gmail.com>
Signed-off-by: Michael Niedermayer <michael@niedermayer.cc>
(cherry picked from commit 3bf142c773)
Signed-off-by: Michael Niedermayer <michael@niedermayer.cc>

cmdutils.h

@@ -61,6 +61,11 @@ void register_exit(void (*cb)(int ret));
  */
 void exit_program(int ret) av_noreturn;
 
+/**
+ * Initialize dynamic library loading
+ */
+void init_dynload(void);
+
 /**
  * Initialize the cmdutils option system, in particular
  * allocate the *_opts contexts.