Memory allocation fails in R 2.2.1 and R 2.3.0 on SGI Irix, (PR#8862)

Dear R developers,

We have a big SGI Origin computation server with 32 cpu's and 64 Gb of
RAM. In R 2.0.0 we could run large jobs, allocating 8 Gb of RAM was not
a problem, for example by running:

 > v1 <- seq(1,2^29)
 > v2 <- seq(1,2^29)
 > v3 <- seq(1,2^29)
 > v4 <- seq(1,2^29)

This yields an R process, consuming about 8 Gb of RAM:
      PID       PGRP USERNAME PRI  SIZE   RES STATE    TIME WCPU% CPU% COMMAND
   177484     177484 mirjam    20 8225M 8217M sleep    1:18  29.3 0.00 R

After upgrading from R 2.0.0 to R 2.2.1, we cannot allocate more than
about 1300 M of memory, as shown below:

 > v1 <- seq(1,2^29)

 Error: cannot allocate vector of size 2097152 Kb

 > v1 <- seq(1,2^28)
 > v2 <- seq(1,2^27)

 Error: cannot allocate vector of size 524288 Kb

 > v2 <- seq(1,2^25)
 > v3 <- seq(1,2^24)
 > v4 <- seq(1,2^23)
 > v5 <- seq(1,2^22)

 Error: cannot allocate vector of size 16384 Kb

 > v5 <- seq(1,2^21)
 > v6 <- seq(1,2^20)
 > v7 <- seq(1,2^19)
 > v8 <- seq(1,2^18)
 > q()

 Save workspace image? [y/n/c]: n
Upgrading to R 2.3.0 yields the same results.
This yields an R executable taking 1284M of RAM, refusing to allocate
more RAM, with about 30Gb free on the machine.