package windows: add a patch to add -DDLL_EXPORT for libmecab.dll

We don't change MeCab version and don't change build script after
releasing the previous version... Why is the patch needed...?
package windows: use ruby-mode.el style multi-line Array literal
package windows: disable KyTea
package windows: disable libedit support
package windows: bundle libgcc_s_seh-1.dll instead of libgcc_s_sjlj-1.dll for x64
doc: write document in English
doc: update po
doc: remove obsolete entries
doc: write document in English
doc: use "true" instead of "1" for "match all"
doc: fix a typo

    drilldown_limits ->
    drilldown_limit
Fix a bug that similar search doesn't use IDF for choosing target tokens

It used token ID instead of IDF.

[groonga-dev,02731]

Reported by Satoshi Mitani. Thanks!!!
Fold a long line
Fix a crash bug when deleting a record

If the table of the record has _key and _key is indexed from two or more
index columns, deleting causes a crash.
doc: add missing GitHub issue number and contributor infomation
deb: add missing remarkable changes about Groonga 4.0.5
deb: use product name as upstream
deb: don't repeat "Copyright" in Copyright field

Reported by Hideki Yamane. Thanks!!!
deb: add description about the complete text of GPL on Debian

Reported by Hideki Yamane. Thanks!!!
deb: add people who contribute to deb packaging

Reported by Hideki Yamane. Thanks!!!