Add shell null to else block

MinGW-W64-builds-4.2.0 shell doesn't like the empty else blocks.
Update build instructions for db4.8 on Debian and Unix
Merge pull request #3752

5d5b0d2 Add shell null to else block (Wil Bown)
Transifex pull pre-0.9.0rc2
Merge pull request #3761

a270ca2 Transifex pull pre-0.9.0rc2 (Wladimir J. van der Laan)
Merge pull request #3760 from ian-kelling/master

Update build instructions for db4.8 on Debian and Unix