Added missing <use-retval/>-tag to strdup()-like functions. In case the return value is not taken in account, a logical error is revealed.

cfg/gtk.cfg

@@ -18088,6 +18088,7 @@
   <function name="g_strdup">
     <noreturn>false</noreturn>
     <returnValue type="gchar *"/>
+    <use-retval/>
     <arg nr="1">
       <not-null/>
       <not-uninit/>

cfg/posix.cfg

@@ -701,6 +701,7 @@ The obsolescent function 'usleep' is called. POSIX.1-2001 declares usleep() func
   <function name="strdup">
     <noreturn>false</noreturn>
     <returnValue type="char *"/>
+    <use-retval/>
     <arg nr="1">
       <not-null/>
       <not-uninit/>
@@ -711,6 +712,7 @@ The obsolescent function 'usleep' is called. POSIX.1-2001 declares usleep() func
   <function name="strndup">
     <noreturn>false</noreturn>
     <returnValue type="char *"/>
+    <use-retval/>
     <arg nr="1">
       <not-null/>
       <not-uninit/>
@@ -725,6 +727,7 @@ The obsolescent function 'usleep' is called. POSIX.1-2001 declares usleep() func
   <function name="wcsdup">
     <noreturn>false</noreturn>
     <returnValue type="wchar_t *"/>
+    <use-retval/>
     <arg nr="1">
       <not-null/>
       <not-uninit/>

cfg/windows.cfg

@@ -2154,6 +2154,7 @@ HFONT CreateFont(
     unsigned char *_mbsdup(const unsigned char *strSource);-->
   <function name="_strdup,_wcsdup,_mbsdup,_tcsdup">
     <noreturn>false</noreturn>
+    <use-retval/>
     <arg nr="1">
       <not-null/>
       <not-uninit/>
@@ -2163,6 +2164,7 @@ HFONT CreateFont(
        wchar_t *_wcsdup_dbg(const wchar_t *strSource, int blockType, const char *filename, int linenumber);-->
   <function name="_strdup_dbg,_wcsdup_dbg,_tcsdup_dbg">
     <noreturn>false</noreturn>
+    <use-retval/>
     <arg nr="1">
       <not-null/>
       <not-uninit/>