fixed x_integer handling for 64-bit

DB2 (erroneously?) assumes a SQL_C_LONG is a 32-bit integer and
defines SQLINTEGER accordingly.  Since a long integer is likely 64
bits on a 64-bit platform, using 'SQLINTEGER' instead of 'long' makes
more sense.
eliminated compiler warnings
fix to allow a statement to be executed multiple times

- close the cursor if one is open
- do not clear parameter bindings between executions
report attempt to bind use elements both by position and name
provide atomic transaction support even when autocommit is enabled
a SQL_SUCCESS_WITH_INFO return code should not result in an exception
freeing a statement automatically closes the cursor and releases column buffers
added result verification and incorporated common tests into the db2 backend tests
sqlState was losing the supplied message text
added implementation of get_affected_rows to the db2 backend
find the 32-bit libraries when building against a 32/64-bit installation of db2
Merge pull request #97 from toonen/db2-patches

DB2 backend patches