individual port, introduce a new variable for bsd.port.mk, VMEM_WARNING.
By setting this variable to `Yes', the user is given a warning about the
virtual memory requirements just before the pre-build stage.
o Also give some examples for different shells for what to do about
it, and mention login.conf(5). bash, for example, has a confusing
-v flag to ulimit.
o Document this in bsd.port.mk.5
espie@ ok
Porters: please make sure you use bsd.port.mk 1.75 or later when
updating ports. That version of the makefile adds all sums. Previous
versions of the makefile will still work for people installing ports.
