Add a capcity member for lists

This is to keep track of the amount that we have allocated for mutable
lists.

Author: d-torrance

M2/Macaulay2/d/actors5.d

@@ -516,7 +516,8 @@ examine(e:Expr):Expr := (
 	  << "basic list:" << endl
 	  << " length: " << length(s.v) << endl
 	  << " hash: " << s.hash << endl
-	  << " mutable: " << s.Mutable << endl;
+	  << " mutable: " << s.Mutable << endl
+	  << " capacity: " << s.capacity << endl;
 	  nullE)
      is s:SpecialExpr do (
 	  stdIO

M2/Macaulay2/d/basic.d

@@ -99,7 +99,7 @@ export seq(e:Expr):Expr := Expr(Sequence(e));
 export seq(e:Expr,f:Expr):Expr := Expr(Sequence(e,f));
 export seq(e:Expr,f:Expr,g:Expr):Expr := Expr(Sequence(e,f,g));
 export list(classs:HashTable,a:Sequence,is_mutable:bool):Expr := (
-     r := List(classs,a,hash_t(0),is_mutable);
+     r := List(classs,a,hash_t(0),is_mutable, length(a));
      Expr(sethash(r)));
 export list(classs:HashTable,a:Sequence):Expr := list(classs, a, false);
 export list(a:Sequence):Expr := list(listClass, a);

M2/Macaulay2/d/parse.d

@@ -312,7 +312,8 @@ export List := {+
      Class:HashTable,
      v:Sequence,
      hash:hash_t,
-     Mutable:bool
+     Mutable:bool,
+     capacity:int -- amount of allocated memory (for mutable lists)
      };
 
 export Error := {+