4235 - fix a build issue for Apple clang 900.0.38

The trouble with rewriting 'unused' to '__attribute__(unused)' is that
if we happen to deliberately introduce '__attribute__(unused)' somehow,
say in the standard headers, then it gets expanded twice to '__attribute__(__attribute__(unused))'.
So we switch to a synonym.

001help.cc

@@ -157,7 +157,7 @@ void initialize_signal_handlers() {
   sigaction(SIGABRT, &action, NULL);  // assert() failure or integer overflow on linux (with -ftrapv)
   sigaction(SIGILL,  &action, NULL);  // integer overflow on OS X (with -ftrapv)
 }
-void dump_and_exit(int sig, unused siginfo_t* dummy1, unused void* dummy2) {
+void dump_and_exit(int sig, vestigial siginfo_t* dummy1, vestigial void* dummy2) {
   switch (sig) {
     case SIGABRT:
       #ifndef __APPLE__
@@ -256,7 +256,7 @@ using std::cerr;
 #include <string>
 using std::string;
 
-#define unused  __attribute__((unused))
+#define vestigial  __attribute__((unused))
 
 #include <algorithm>
 using std::min;

003trace.cc

@@ -202,7 +202,7 @@ bool trace_contains_errors() {
 :(before "End Types")
 struct end {};
 :(code)
-ostream& operator<<(ostream& os, unused end) {
+ostream& operator<<(ostream& os, vestigial end) {
   if (Trace_stream) Trace_stream->newline();
   return os;
 }

030container.cc

@@ -761,7 +761,7 @@ Transform.push_back(expand_type_abbreviations_in_containers);  // idempotent
 :(code)
 // extremely inefficient; we process all types over and over again, once for every single recipe
 // but it doesn't seem to cause any noticeable slowdown
-void expand_type_abbreviations_in_containers(unused const recipe_ordinal r) {
+void expand_type_abbreviations_in_containers(vestigial const recipe_ordinal r) {
   for (map<type_ordinal, type_info>::iterator p = Type.begin();  p != Type.end();  ++p) {
     for (int i = 0;  i < SIZE(p->second.elements);  ++i)
       expand_type_abbreviations(p->second.elements.at(i).type);

056shape_shifting_recipe.cc

@@ -205,7 +205,7 @@ bool contains_type_ingredient_name(const type_tree* type) {
   return contains_type_ingredient_name(type->left) || contains_type_ingredient_name(type->right);
 }
 
-int number_of_concrete_type_names(unused const instruction& inst, recipe_ordinal r) {
+int number_of_concrete_type_names(vestigial const instruction& inst, recipe_ordinal r) {
   const recipe& caller = get(Recipe, r);
   int result = 0;
   for (int i = 0;  i < SIZE(caller.ingredients);  ++i)
@@ -223,7 +223,7 @@ int number_of_concrete_type_names(const type_tree* type) {
        + number_of_concrete_type_names(type->right);
 }
 
-int number_of_type_ingredients(unused const instruction& inst, recipe_ordinal r) {
+int number_of_type_ingredients(vestigial const instruction& inst, recipe_ordinal r) {
   const recipe& caller = get(Recipe, r);
   int result = 0;
   for (int i = 0;  i < SIZE(caller.ingredients);  ++i)

073scheduler.cc

@@ -312,7 +312,7 @@ def f2 [
 +error: f2: divide by zero in '3:num <- divide-with-remainder 4, 0'
 -error: f2: divide by zero in '4:num <- divide-with-remainder 4, 0'
 
-:(after "operator<<(ostream& os, unused end)")
+:(after "operator<<(ostream& os, vestigial end)")
   if (Trace_stream && Trace_stream->curr_label == "error" && Current_routine) {
     Current_routine->state = COMPLETED;
   }