ast_node: Add new talloc-based new()

And use the talloc-based new for all of the ast objects created by the
parser.  This closes a lot of memory leaks, and will allow us to use
these ast objects as talloc parents in the future, (for things like
exec_nodes, etc.).

This closes 164 leaks in the glsl-orangebook-ch06-bump.frag test:

	total heap usage: 55,623 allocs, 14,553 frees
	(was 14,389 frees)

1 files changed, 19 insertions, 0 deletions

diff --git a/ast.h b/ast.h
index 782e2c7ce7..de300e719c 100644
--- a/ast.h
+++ b/ast.h
@@ -36,6 +36,25 @@ struct YYLTYPE;
 
 class ast_node {
 public:
+   /* Callers of this talloc-based new need not call delete. It's
+    * easier to just talloc_free 'ctx' (or any of its ancestors). */
+   static void* operator new(size_t size, void *ctx)
+   {
+      void *node;
+
+      node = talloc_size(ctx, size);
+      assert(node != NULL);
+
+      return node;
+   }
+
+   /* If the user *does* call delete, that's OK, we will just
+    * talloc_free in that case. */
+   static void operator delete(void *table)
+   {
+      talloc_free(table);
+   }
+
    virtual void print(void) const;
    virtual ir_rvalue *hir(exec_list *instructions,
 			  struct _mesa_glsl_parse_state *state);