Add cppversion as makegen config parameter

- Add cppversion as makegen config parameter, making it possible to
  specify which cpp version to use
- General cleanup of unused code

makegen.xml

@@ -1,5 +1,6 @@
 <makegen>
   <configuration name="Release">
+    <cppversion>c++17</cppversion>
     <outputdir>bin/Release/</outputdir>
     <outputname>makegen</outputname>
     <outputtype>executable</outputtype>
@@ -9,6 +10,7 @@
   <configuration name="Debug">
     <cflag>-g3</cflag>
     <cflag>-w</cflag>
+    <cppversion>c++17</cppversion>
     <define>_DEBUG</define>
     <outputdir>bin/Debug/</outputdir>
     <outputname>makegen</outputname>
@@ -17,5 +19,5 @@
     <srcdir>src/</srcdir>
   </configuration>
   <target>Release</target>
-  <version>v1.3.10</version>
+  <version>v1.3.11</version>
 </makegen>