Do not write calculated advance costs into ruleset.

Originally reported by Sveinung Kvilhaugsvik (sveinung@gna)

See gna bug #22287 & bug #22288

git-svn-id: svn://svn.gna.org/svn/freeciv/trunk@25463 a0f10bec-cc02-0410-94fc-a9cfff90b4cd
Remove advance_by_flag() and techs_with_flag_iterate macro couple.

See gna patch #4909

git-svn-id: svn://svn.gna.org/svn/freeciv/trunk@25464 a0f10bec-cc02-0410-94fc-a9cfff90b4cd
Send the real cost of the researching advance (after tech leakage, EFT_TECH_COST_FACTOR,
and AI cost reduction) to the clients.

See gna bug #22062

git-svn-id: svn://svn.gna.org/svn/freeciv/trunk@25465 a0f10bec-cc02-0410-94fc-a9cfff90b4cd
Rename and move player_research_step() to research_goal_step()

See gna patch #4911

git-svn-id: svn://svn.gna.org/svn/freeciv/trunk@25466 a0f10bec-cc02-0410-94fc-a9cfff90b4cd