DBase File locking issues (PR#20441)

[tridge at linuxcare.com]

> >   locking not supported? returning True
> 
> ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
> This above is old crufty code that is no longer needed; it was
> used for systems that didn't have fcntl locks. We now check
> for these at compile time and refuse to run. I'm removing
> this asap.

be careful. This code was for systems that support locks on some
filesystems but not others. For example, many Linux systems don't
support fcntl locks at all on NFS fileystems. If you compile on ext2
then run Samba on NFS removing that code will cause Samba to fail
completely. That is quite a common setup.

At the very least we would need to add docs advising users to use
"locking = no" on filesystems that don't support fcntl locks, but I'd
prefer to automate that with a runtime test. 

Cheers, Tridge