Description of problem:

$Summary as a result of memsize trying to malloc >3GB on 32-bit kernels

Steps to Reproduce:
1.find a 32-bit kernel with >~3GB of RAM
2.run memsize 3000
  
Actual results:

<snip>
$lmbench_dir/memsize $mem
++ /usr/lib/lmbench/bin/i686-pc-linux-gnu/memsize 3287
malloc: Cannot allocate memory
</snip>

the side effect causes this series of events; which nets us testing 500MB on a
4GB+ box:

<snip>
+ '[' -z '' ']'
+ echo 'WARNING: memsize failed! Using 80% of reported free RAM'
WARNING: memsize failed! Using 80% of reported free RAM
awk '/^MemFree:/ {print $2}' /proc/meminfo
++ awk '/^MemFree:/ {print $2}' /proc/meminfo
+ local freemem=1441
+ avail=1152
+ echo '1152MB available'
1152MB available
+ local MB=576
</snip>

Expected results:

Full testing of available ram; it would of been nice if memsize would fork to
properly flush the buffers cache's etc.; however the alternative is to make
MEMORY2 smarter and have it allocate no larger than 2.8 or so GB per process and
flush RAM out that way; at least on 32-bit kernels; another possibility might be
to add free + buffers + cache; minus some gap amount and try to test that; if we
can't flush the buffers and cache's at least mostly then something went wrong I
would guess.