Lua: Replace listenv() with nef's fce()
I think we can have this even in d3f S3_0, after all; just remove old listenv(), bring in fce() named as listenv() and modified to have same fingerprint as old listenv() had. Then it would be, compatibility wise, drop-in replacement.
New patch version based on new fce() version by nef
In http://forum.freeciv.org/f/viewtopic.php?f=14&t=91972&p=103953#p103947 nef lists ways that current listenv() may hang or crash, and provides a function called fce() as a replacement.
Port nef's fce() to mainstream freeciv. Replace current listenv() implementation with a trivial wrapper for fce() (to keep function named listenv() around for compatibility)