Clean up env_var_table_t. Switch from storing var_uni_entry_t* to var_uni_entry_t. Various other cleanups.

reader.cpp

@@ -668,7 +668,7 @@ int reader_reading_interrupted()
     {
         reader_exit(1, 0);
         parser_t::skip_all_blocks();
-        // We handled the interrupt ourselves, our caller doesn't need to 
+        // We handled the interrupt ourselves, our caller doesn't need to
         // handle it.
         return 0;
     }