elaborate prepared_stmt_bind_static_text to illustrate with_c_str() bug #95

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extra : source : adc9264cba0d828aaf7815c538174ea7b74f1c49
fix string lifetime in StaticText case of bind_param.
fixes: #95

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extra : source : 89e2a09be1e08cc8ddb3c5688bae670ce0d2ab53
Merge pull request #97 from dckc/bind-static-text-95

fix StaticText lifetime bug in bind_param (#95)