ps_mem.py: support Linux kernels >= version 3.0
ps_mem.py: support Linux kernels >= version 3.0

* scripts/ps_mem.py: Parse 2 digit kernel versions (3.0)
correctly.  Also recognise that kernels >= 3.0 are accurate.

pixelb/ps_mem,mitchty/ps_mem,nubark/ps_mem,knoxxs/ps_mem,shekkbuilder/ps_mem,gdm/ps_mem