Move source reading into a function

gcc/elna-generic.cc

@@ -100,7 +100,7 @@ namespace elna::gcc
     }
 
     std::deque<std::unique_ptr<boot::error>> do_semantic_analysis(const char *path,
-            std::unique_ptr<boot::program>& ast, std::shared_ptr<boot::symbol_table> info_table,
+            const std::unique_ptr<boot::program>& ast, std::shared_ptr<boot::symbol_table> info_table,
             std::shared_ptr<symbol_table> symbols, std::unordered_map<std::string, tree>& unresolved)
     {
         boot::declaration_visitor declaration_visitor(path, info_table);