configure.ac: add missing sphinx error message for OSX with Homebrew system
expr: suppress unused variable 'e' warning

`grn_expr *e = (grn_expr *)expr` is defined in `grn_expr_alloc_const()` internal.
Merge pull request #197 from cosmo0920/suppress-warning-expr

expr: suppress unused variable 'e' warning

Patch by cosmo0920. Thanks!!!
configure.ac: enclosed in double quote entirely

PATH=`brew --prefix gettext`"/bin:\$PATH"
PATH="`brew --prefix gettext`/bin:\$PATH"
     ^<---------------------|
Merge pull request #198 from cosmo0920/doc-configure-error-msg-OSX

configure.ac: add missing sphinx error message for OSX with Homebrew system

Patch by cosmo0920. Thanks!!!
Add account information on ConoHa
Use "OS X" form

Because "OS X" is used since 10.7.
fedora: ensure that log directory exists on startup
doc: write in English about Users table
doc en: translate into English about Comments table
doc en: translate into English about HashTags table
doc en: translate into English about bigram table
doc en: update example data about loading data section

TODO: improve more suitable examples for foreigner
doc en: translate into English about loading data description
doc en: add missing space

Without this change, it doesn't regarded as part of groonga commands.
doc en: update query in English
doc en: update tutorial examples
mrb ctx: cache singleton object
mrb: define error classes

anzu-query-replace-regexp is my friend. :-)
mrb expr: bind grn_expr_alloc_const()