Library configuration validation: Enhance relaxng file, fix *.cfg files. (#1685)

This fixes https://trac.cppcheck.net/ticket/8985 at least for the
function configuration.
Errors in configuration files found by the new relaxng file are fixed.

cfg/cppcheck-cfg.rng

@@ -69,13 +69,26 @@
           <ref name="DATA-EXTNAME"/>
         </attribute>
 
-        <zeroOrMore>
-          <choice>
+        <interleave>
+          <optional>
             <element name="noreturn"><ref name="DATA-BOOL"/></element>
+          </optional>
+          <optional>
             <element name="pure"><empty/></element>
+          </optional>
+          <optional>
             <element name="const"><empty/></element>
+          </optional>
+          <optional>
             <element name="ignorefunction"><ref name="DATA-BOOL"/></element>
+          </optional>
+          <optional>
             <element name="leak-ignore"><empty/></element>
+          </optional>
+          <optional>
+            <element name="use-retval"><empty/></element>
+          </optional>
+          <optional>
             <element name="returnValue">
               <optional>
                 <attribute name="type">
@@ -91,7 +104,8 @@
               </optional>
               <text/>
             </element>
-            <element name="use-retval"><empty/></element>
+          </optional>
+          <optional>
             <element name="formatstr">
               <optional>
                 <attribute name="scan"><ref name="DATA-BOOL"/></attribute>
@@ -101,6 +115,8 @@
               </optional>
               <empty/>
             </element>
+          </optional>
+          <optional>
             <element name="warn">
               <attribute name="severity">
                 <choice>
@@ -132,6 +148,8 @@
               </optional>
               <text/>
             </element>
+          </optional>
+          <zeroOrMore>
             <element name="arg">
               <attribute name="nr">
                 <choice>
@@ -190,8 +208,8 @@
                 </choice>
               </zeroOrMore>
             </element>
-          </choice>
-        </zeroOrMore>
+          </zeroOrMore>
+        </interleave>
       </element>
 
       <element name="markup">

cfg/motif.cfg

@@ -146,7 +146,6 @@
     <noreturn>false</noreturn>
     <use-retval/>
     <returnValue type="Display *"/>
-    <use-retval/>
     <arg nr="1">
       <not-uninit/>
     </arg>

cfg/windows.cfg

@@ -3650,9 +3650,8 @@ HFONT CreateFont(
     <use-retval/>
     <pure/>
     <noreturn>false</noreturn>
-    <returnValue type="size_t"/>
     <leak-ignore/>
-    <returnValue>strlen(arg1)</returnValue>
+    <returnValue type="size_t">strlen(arg1)</returnValue>
     <arg nr="1">
       <not-null/>
       <not-uninit/>
@@ -3666,11 +3665,10 @@ HFONT CreateFont(
   <!-- size_t _mbstrlen( const char *str ); -->
   <function name="_mbslen,_mbstrlen,_tcslen,_tcsclen">
     <use-retval/>
-    <returnValue type="size_t"/>
     <pure/>
     <noreturn>false</noreturn>
     <leak-ignore/>
-    <returnValue>strlen(arg1)</returnValue>
+    <returnValue type="size_t">strlen(arg1)</returnValue>
     <arg nr="1">
       <not-null/>
       <not-uninit/>

cfg/wxwidgets.cfg

@@ -7521,7 +7521,6 @@
     <arg nr="1">
       <not-uninit/>
     </arg>
-    <use-retval/>
     <arg nr="2">
       <not-uninit/>
     </arg>