[perl] fix compatibility issue with flock_server on BONE

[brecht]

This is required to build a copy of Perl for BONE with dynamically linked extensions.

First try to build with other versions of GCC (differences in linking?)

Ingo: The only thing that the flock() support changes is defining
close() to flock_close() and dup2() to flock_dup2(). After a little
communication with the server, the flock_*() versions just call the
original functions.

You could try not to link against libflock.so, but keep the macro
definitions in place, and define the flock_*() functions (in beos.c) to
call the close()/dup2() directly. Then you'd at least learn, if the macro
definitions screw things up.