gnu.cfg: Added support for xstrdup().

cfg/gnu.cfg

@@ -23,6 +23,17 @@
       <valid>0:</valid>
     </arg>
   </function>
+  <!-- char *xstrdup(const char *s); -->
+  <function name="xstrdup">
+    <noreturn>false</noreturn>
+    <returnValue type="char *"/>
+    <use-retval/>
+    <arg nr="1">
+      <not-null/>
+      <not-uninit/>
+      <not-bool/>
+    </arg>
+  </function>
   <!-- void * xcalloc(size_t nitems, size_t size); -->
   <function name="xcalloc">
     <use-retval/>