Cherry-picked several commits from kitagawa_tfont branch

Cherry-picked several commits from kitagawa_tfont branch

c021eb1 - Wed Dec 3 16:06:58 2014 +0900: match option in luatexja-preset.sty.
8156de2 - Wed Dec 3 16:27:15 2014 +0900: updated manuals
96f2016 - Wed Dec 24 21:54:57 2014 +0900: ltjsclasses: \@setfontsize should not set xkanjiskip if
xkanjiskip<=0
fe9ceab - Wed Jan 7 11:06:52 2015 +0900: lltjp-listings.sty: fix \lstinline@
b4be058 - Wed Jan 7 11:19:19 2015 +0900: ... and more
117099f - Thu Jan 8 21:23:52 2015 +0900: lltjp-listings.sty: added 'doubleletterspace' key.
ec6db6e - Fri Jan 9 10:29:29 2015 +0900: Manual: added doubleletterspace'' key.