Fix OUT direction of IN/OUT procedure parameter

Solve issue #81
Bring back convert_from_base() for the input ("use") parameters (removed
as unnecessary in SHA: 22e740a6)
Add comments with clarification why these conversion is necessary, by
design
Split Oracle's test7 into three separate tests
Tests pass for Oracle XE 10g.
Remove auto keyword left over by accident
Merge pull request #88 from mloskot/issue-81

Fix OUT direction of IN/OUT procedure parameter