Added utility to determine if a unit is contained (transported directly or
indirectly) within a transport.

See gna patch #4693

git-svn-id: svn://svn.gna.org/svn/freeciv/trunk@24901 a0f10bec-cc02-0410-94fc-a9cfff90b4cd
Don't send out of sight for transported units when moving their transporter.

Reported anonymously

See gna bug #21899

git-svn-id: svn://svn.gna.org/svn/freeciv/trunk@24904 a0f10bec-cc02-0410-94fc-a9cfff90b4cd
Even if errors are detected, do not return before unloading the cargo from a
transport. Else, there could potentially freed unit pointers in the cargo unit
list.

From an anonymous report

See gna bug #21899

git-svn-id: svn://svn.gna.org/svn/freeciv/trunk@24907 a0f10bec-cc02-0410-94fc-a9cfff90b4cd
Rewrite hash table module to use open hashing. Collision
resolution is now done by separate chaining with linked lists.

Reported by Marko Lindqvist (cazfi@gna)

See bug #21988

git-svn-id: svn://svn.gna.org/svn/freeciv/trunk@24910 a0f10bec-cc02-0410-94fc-a9cfff90b4cd
Optimize the priority queues.

See gna patch #4701

git-svn-id: svn://svn.gna.org/svn/freeciv/trunk@24911 a0f10bec-cc02-0410-94fc-a9cfff90b4cd
Reduce the number of calls to priority queue functions and add
some extra checks to path-finding.

See gna patch #4702

git-svn-id: svn://svn.gna.org/svn/freeciv/trunk@24912 a0f10bec-cc02-0410-94fc-a9cfff90b4cd
Remove the usage of same_pos() from path-finding.

See gna patch #4703

git-svn-id: svn://svn.gna.org/svn/freeciv/trunk@24913 a0f10bec-cc02-0410-94fc-a9cfff90b4cd