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GitHub #22
Use <...> style for variable in error/log message

Because this style is used in this project.

Fix #22
Add `:id => true` option to Groonga::Table::KeySupport#delete

GitHub #23:

    `Groonga::Table::KeySupport#delete` accepts both ID and
    key. If passed value is integer, it is handled as ID.
    But we can use `Int32` as key. In the case, we can't
    delete a record by key.

    Add `Groonga::Table::KeySupport#delete(id, :id => true)`
    API. It introduces a backward incompatibility. But it is
    OK because the current API is a bug.
Add missing `:id => true` option

It follows the change by commit 06e06f7ef5b754ee65f34169108e4631f1dad300
Fix a bug that Groonga::Array#delete fails

Caused by commit 9b23b1ef21195847fe0e687cb660552f4027f87d
Indent
Remove needless "Groonga::"
windows: disable debug flags