httpd: set header_only flag when body is empty
test: follow syntax error message improvement
test: omit a crashed test on Travis CI

Why?
test: really follow syntax error message improvement
test: really really follow syntax error message improvement

Sorry...
test: omit crash test

Why?
Support inspecting uvector
Fix return value
Initialize missing flags field
Ensure initializing format
test: follow uvector inspect change
doc ja: translate
doc: add a missing "s"
test: fix ">" position
doc: use "Groonga" notation
doc: fix a typo
doc: don't use one line JSON style
doc: fix a link
doc: fix a typo
doc: don't use one line JSON style