Fix two compile errors on AIX.
Missing handling of "close" errors

When backing up on a CIFS target (others?), a full (remote) file system
is not detected until close() returns (returning -1 and setting errno).
However, the return value is not verified, and the incorrect write
operation is not detected. The final job result is "ok", but the volume
files are small or empty.

Fixes #233: Missing handling of "close" errors

Signed-off-by: Marco van Wieringen <marco.van.wieringen@bareos.com>
Fix compiling without any compression.

When you don't have zlib, lzo2 or fastlz the code didn't compile
due to one missing dummy prototype. And two dummy prototypes had
wrong typed arguments to their non dummy counterparts.