Store inode when reading /proc/*/smaps in _pslinux.py/get_memory_maps()

At the moment, the function get_memory_maps() in the Linux implementation 
_pslinux.py, correctly parses the content of /proc/<pid>/smaps and stores some 
of the memory maps data in a container.

Unfortunately, it does not store the inode, although it is correctly parsed 
from first_line.

This is specifically necessary with SYSV00000000 maps, because their path names 
are not unique.

It would be great to store the inode as a new item in the returned container. 
It does not imply changes to existing applications.

On the other hand, I do not know how this can be emulated on other operating systems.