Fixed #2776 (false negative: usage of unitialized pointer (closedir))

cfg/posix.cfg

@@ -2,7 +2,8 @@
 <def>
   <function name="usleep"> <noreturn>false</noreturn> <arg nr="1"><not-bool/><valid>0-999999</valid></arg> </function>
   <function name="_exit"> <noreturn>true</noreturn> </function>
-  
+  <function name="closedir">  <arg nr="1"><formatstr/><not-uninit/><not-null/></arg> </function>
+
   <resource>
     <dealloc>close</dealloc>
     <alloc init="true">socket</alloc>