std.cfg and windows.cfg: Improved support for <use-retval/> for functions like ftell(), [f]get[w]c().

cfg/std.cfg

@@ -832,6 +832,7 @@
   <function name="fgetc,std::fgetc">
     <noreturn>false</noreturn>
     <leak-ignore/>
+    <use-retval/>
     <arg nr="1">
       <not-null/>
       <not-uninit/>
@@ -841,6 +842,7 @@
   <function name="fgetwc,std::fgetwc">
     <noreturn>false</noreturn>
     <leak-ignore/>
+    <use-retval/>
     <arg nr="1">
       <not-null/>
       <not-uninit/>
@@ -1408,6 +1410,7 @@
   <function name="getc,std::getc">
     <noreturn>false</noreturn>
     <leak-ignore/>
+    <use-retval/>
     <arg nr="1">
       <not-null/>
       <not-uninit/>
@@ -1417,6 +1420,7 @@
   <function name="getwc,std::getwc">
     <noreturn>false</noreturn>
     <leak-ignore/>
+    <use-retval/>
     <arg nr="1">
       <not-null/>
       <not-uninit/>

cfg/windows.cfg

@@ -2095,10 +2095,13 @@ HFONT CreateFont(
       <not-uninit/>
     </arg>
   </function>
-  <!-- __int64 _ftelli64(FILE *stream); -->
-  <function name="_ftelli64">
+  <!-- __int64 _ftelli64(FILE *stream); 
+         long _ftell_nolock(FILE *stream);  
+       __int64 _ftelli64_nolock(FILE *stream); -->
+  <function name="_ftelli64,_ftell_nolock,_ftelli64_nolock">
     <noreturn>false</noreturn>
     <leak-ignore/>
+    <use-retval/>
     <arg nr="1">
       <not-null/>
       <not-uninit/>

test/cfg/std.c

@@ -78,7 +78,7 @@ void nullpointer(int value)
     // cppcheck-suppress nullPointer
     feof(0);
     // cppcheck-suppress nullPointer
-    fgetc(0);
+    (void)fgetc(0);
     // cppcheck-suppress nullPointer
     fclose(0);
     // cppcheck-suppress ignoredReturnValue
@@ -265,7 +265,7 @@ void uninit_fgetc(void)
 {
     FILE *fp;
     // cppcheck-suppress uninitvar
-    fgetc(fp);
+    (void)fgetc(fp);
 }
 
 void uninit_fgetpos(void)