Fix the MSpace function, which needed to accept the INT as intput, not
string. Add test to verify output.
Fix the handling of the null/negative values with the LONGTEXT settings.
Add more corner case tests.
merge tjoneslo: Fix the MSpace function, which needed to accept the INT as intput, not string

Merge pull request #1042 from tjoneslo/sql-layer/func-space-fixes
https://github.com/FoundationDB/sql-layer/pull/1042