Log Message:
Overhaul ja-mh package, update to ja-mh6-3.05.

- Based on mh-6.8.4-JP-3.05 + four official patches.
- Update MASTER_SITES and HOMEPAGE.

- make vmh(1) build again.
- specify proper link option; build again after introduce
  of "toolchain wrappers."
- improve patch to concat.c.

Great thanks to Masanori Mikawa on tech-pkg-ja.