Updates so that packages are installed into /usr/local/xpm/pkg with a
view to binary portability.
Make openssl version semver compatible and add verify false to zlib
package.
Respect the false value for *verify* used to indicate that a package
does not have any verification commands.
Implement the pack command for iox(1).
Document the location for tarballs created using the pack command of
iox(1).
Add binary expect and verify commands to ncurses.
Add verify false for readline package.
Add binary expect and verify commands to the pth package.
Add sha checksum and verify false to gc (bdw-gc) package.
Update libevent and tmux package descriptors.
Update grep package descriptor.
Update pcre package descriptor.
Merge branch 'feature/sandbox' into develop