set default memheap start address to use one returned from memallocator
on 32bit system kernel may have issue because of this:
CONFIG_STRICT_DEVMEM kernel option which "prevents user space access to physical memory above 1MB"
fixed by Roman, reviewed by Igor/Miked
cmr=v1.8.1:reviewer=ompi-rm1.8
This commit was SVN r31331.
490d28e2d4