posix.cfg: Improved configuration for dlopen() and dlclose(). Ensure the return value is taken into account for dlopen() and leak-ignore flag is not present for dlopen() and dlclose().

cfg/posix.cfg

@@ -348,7 +348,7 @@
   <!-- void *dlopen(const char *file, int mode); -->
   <function name="dlopen">
     <noreturn>false</noreturn>
-    <leak-ignore/>
+    <use-retval/>
     <returnValue type="void*"/>
     <arg nr="1" direction="in">
       <not-uninit/>
@@ -376,7 +376,6 @@
   <!-- int dlclose(void *handle); -->
   <function name="dlclose">
     <noreturn>false</noreturn>
-    <leak-ignore/>
     <returnValue type="int"/>
     <arg nr="1">
       <not-uninit/>