style: minor changes

* src/complain.c: Space changes.
* src/reader.c: Comment changes.
Avoid && in assertions.
* src/location.c: Move comments to...
* src/location.h: here.
* src/symlist.h, src/symlist.c: Create a pseudo section for members
that apply to the rule.

src/symlist.h

@@ -50,6 +50,9 @@ typedef struct symbol_list
   } content;
   location location;
 
+  /* Named reference. */
+  named_ref *named_ref;
+
   /* Proper location of the symbol, not all the rule */
   location sym_loc;
 
@@ -64,19 +67,21 @@ typedef struct symbol_list
   struct symbol_list *midrule_parent_rule;
   int midrule_parent_rhs_index;
 
+  /* ---------------------------------------------- */
+  /* Apply to the rule (attached to the LHS only).  */
+  /* ---------------------------------------------- */
+
+  /* Precedence/associativity.  */
+  symbol *ruleprec;
+
   /* The action is attached to the LHS of a rule, but action properties for
    * each RHS are also stored here.  */
   code_props action_props;
 
-  /* Precedence/associativity.  */
-  symbol *ruleprec;
   int dprec;
   int merger;
   location merger_declaration_location;
 
-  /* Named reference. */
-  named_ref *named_ref;
-
   /* The list.  */
   struct symbol_list *next;
 } symbol_list;