mcoverlayfs code is now unused (technically should work on top of the
soft emulation but not well tested, and untested unused code is bad).
Remove it.
Left the unshare/bind_mount_recursive code in mcexec in a new
MCEXEC_BIND_MOUNT ifdef (only in config.h.in directly to discourage use.
it disables the ioctl as well, but the main code is still compiled to
keep up to date with linux api changes... although it's using kallsyms
lookup so it does not validate much more than "the symbol still exists")
I honestly think this should go as well (people who would want to use it
are root and could do it manually), but will give up for now.
Change-Id: I832b6a8ab19e24ed67a1a5044b1c6c32381ae0aa
791e8c2114