mmap() test in Zmailer configure

["Andrew P. Kokarev" <andrew@skfgvc.pyatigorsk.su>]

I now tried to make Zmailer on BSD/OS system. There are some problems,
I will post description later.

The first one I want to mention is wrongness of mmap() test.
Configure tries to compile and execute bad code to test it.
It even doesn't compile on BSD/OS 2.0.1 system due to
lseek() with long (as opposed to 64-bit off_t) offset argument.

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Joint stock company "GVC Energeticy", North-Caucasian Branch, Pyatigorsk
Andrew Petrovich Kokarev, postmaster         andrew@skfgvc.pyatigorsk.su