Rename grn_token to grn_token_cursor

Because it's not "token" itself. It generates tokens. We're using
"cursor" for object that returns the next ID by "_next()" function.

So grn_token_cursor name is better for the current grn_token object.
token-filter: use token filter specific callbacks instead of generic callbacks

Generic callbacks are difficult to understand how to use API because
its signature doesn't show what arguments are passed.

Specific callbacks are easy to understand how to use API because its
signature shows what arguments are passed.
dump: support "table_create --token_filters"
table_create: support multiple token filters
dump: check table key type for token_filters

In case of TABLE_NO_KEY, grn_obj_get_info outputs an error message
Merge pull request #215 from naoa/dump-check-key_type

dump: check table key type for token_filters

Patch by Naoya Murakami. Thanks!!!
test: use meaningful name for file name
packages: wait one hour for upping VM

It is for poor spec server.
package yum: add /sbin explicitly for CentOS 5
package rpm: add stop word token filter
package rpm: fix a typo...
packages yum: use absolute path
packages deb: bundle token_filter stop word plugin
Merge pull request #216 from cosmo0920/bundle-token-filter-deb

packages deb: bundle token_filter stop word plugin

Patch by Hiroshi Hatake. Thanks!!!
Fix a bug that url encoding fails if char is unsigned

GitHub: fixes #217
Fix a bug that html mapping fails if char is unsigned

GitHub: fixes #218
Merge pull request #214 from groonga/improve-token-filter-api

Improve token filter API
traivs: try to add -funsigned-char build
deb: add missing license
deb: add license detail of BSD 2 clause