storage: mockup implementation of a SQLITE VFS

Created a SQLITE VFS called "almanah" based in the code by the SQLITE
hackers available in http://www.sqlite.org/vfs.html, example called
test_demovfs.c.

This is the starting point to implement the SQLITE VFS with non-pageable
memory. At the moment, just the code from test_demovfs.c

See Bug #659500 - Prevent the unencrypted database from hitting the disk
https://bugzilla.gnome.org/show_bug.cgi?id=659500