K 10
svn:author
V 7
syntron
K 8
svn:date
V 27
2011-01-21T12:05:37.371233Z
K 7
svn:log
V 185
fix tech tree

* add asserts in add_requirement()
* fix player_invention_reachable() to also check the requirements
* (recursively!)

see gna bug #16852
reported by HanduMan <handuman>

END