Build sqlite3 with usleep(3) support so it does not round all sleeps up to second intervals.

This helps our transaction code tremendously which tries to use
sqlite3_sleep(250) while SQLITE_BUSY is returned
Lower transaction sleep a bit and raise the amount of retries to compensate.

This along with HAVE_USLEEP greatly helps parallel read-only transactions
Convert SQLITE_BUSY retries into a uniform MACRO