Split `presym_table` for reduced program size

Because a structure that is an element of `presym_table` has padding, split
it into individual arrays for name and length.

#### Result (64-bit CPU with full-core gembox)

|        |   mruby    | libmruby.a |
|--------|------------|------------|
| Before | 1,087,444B | 1,476,872B |
| After  | 1,079,340B | 1,469,784B |

1 files changed, 5 insertions, 1 deletions

diff --git a/tasks/presym.rake b/tasks/presym.rake
index 8b18acd75..2efc4d790 100644
--- a/tasks/presym.rake
+++ b/tasks/presym.rake
@@ -33,7 +33,11 @@ MRuby.each_target do |build|
     current_presyms = presym.read_list if File.exist?(presym.list_path)
     update = presyms != current_presyms
     presym.write_list(presyms) if update
-    presym.write_header(presyms) if update || !File.exist?(presym.header_path)
+    mkdir_p presym.header_dir
+    %w[id table].each do |type|
+      next if !update && File.exist?(presym.send("#{type}_header_path"))
+      presym.send("write_#{type}_header", presyms)
+    end
   end
 
   gensym_task.enhance([presym.list_path])