Add license headers

releaseaudit:
     [exec]  !????? /src/test/aop/org/apache/sqoop/mapreduce/SqlServerExportAspect.aj
     [exec]  !????? /src/test/aop/org/apache/sqoop/mapreduce/db/SqlServerImportAspect.aj
     [exec]  !????? /src/test/oraoop/create_users.sql
     [exec] Possible violations found.
     [exec] See /tmp/sqoop-1.4.5.bin__hadoop-2.0.4-alpha/build/filtered-release-audit.log