Added a new GCC mirror site in Japan.

* `gcc/jamfile`: Added a new GCC mirror site in Japan.
* `template/x86_64-unknown-linux-gnu/site-config.jam`: Just tweaked
  quotations etc.
Added workaround for Debian multiarch.

* `template/x86_64-unknown-linux-gnu/gcc-wrapper`: Added workaround for
  Debian multiarch. Because GCC without Debian patches cannot find by
  default libraries that reside in Debian multiarch directories,
  `-rpath-link` options to the directories are required for GCC (and an
  underlying linker) to correctly resolve indirect dependencies among shared
  libraries in link time.
* `template/x86_64-unknown-linux-gnu/g++-wrapper`: Likewise.
* `summary.sh`: Removed the column for `address-model=unspecified`. Added
  rows for Boost.Atomic, Boost.Coroutine, Boost.Lockfree and
  Boost.Multiprecision.