bshell: re-organise build into three separate components

bshell: the front-end binary
bshell.runtime: contains the parser, compiler, and classes needed to run bshell scripts
bshell.core: contains the builtin commandlets and aliases

bshell.runtime/ast/block.c

@@ -0,0 +1,26 @@
+#include <bshell/ast.h>
+
+static enum bshell_status collect_children(
+	struct bshell_ast_node *node,
+	struct bshell_ast_iterator *it)
+{
+	struct bshell_block_ast_node *block = (struct bshell_block_ast_node *)
+		node;
+	fx_queue_entry *cur = fx_queue_first(&block->n_statements);
+	while (cur) {
+		struct bshell_ast_node *child = fx_unbox(
+			struct bshell_ast_node,
+			cur,
+			n_entry);
+		bshell_ast_iterator_enqueue(it, child);
+		cur = fx_queue_next(cur);
+	}
+
+	return BSHELL_SUCCESS;
+}
+
+struct bshell_ast_node_definition block_bshell_ast_node = {
+	.def_id = BSHELL_AST_BLOCK,
+	.def_node_size = sizeof(struct bshell_block_ast_node),
+	.def_collect_children = collect_children,
+};