Have louds tries and token array as values in SystemDictionary

With this CL, SystemDictionary has the louds tries and token array as values instead of pointers.
Benefits with this changes are:
- Locality improves (compiler may optimize code more).
- Indirection is removed when accessing to tries and token array.

Note that this is just a code cleanup.  No behavior change is intended.

Patch from Noriyuki Takahashi.

BUG=none
TEST=unittest


git-svn-id: http://mozc.googlecode.com/svn/trunk@543 a6090854-d499-a067-5803-1114d4e51264