0.12.16

This is a bugfix release.

Changes:

• Fixed the package.path entries in setrequirepath and pdlua_packagepath for Lua 5.3+ compatibility.
• Plugged a memory leak in pdlua_packagepath.
• Added a cpath entry in pdlua_packagepath. We don't need it at present, but we might in the future, and in any case this allows the user to put Lua packages there which involve compiled C modules.
• Updated the link to carvalho's Numeric Lua in the tutorial (there's a newer fork by michal-h21 of that module which works with Lua 5.3+.)