ware_besch.h:  Enter comments related to speed bonus calculation, in prep for revenue rework
Relocate calc_adjusted_speedbonus to ware_besch_t::get_adjusted_speedbonus.  Rewrite to eliminate several bugs in it.  Prepare for unit change.
Merge branch 'ncn-devel' into mail-revenue
Merge branch 'ncn-devel' into mail-revenue
Fix binary search in dingliste.cc to use unsigned arithmetic.
Rework dingliste_t.  Fix null pointer bug caused by death of trees.  Rewrite code to provide much more comprehensible internal interface, and faster code when assertions are turned off.  Revise memory management strategy to save memory in common case.  Most likely eliminate other lurking bugs by virtue of cleaner interface.
Fix missing prototype in previous commit.
Fix more mismatched prototypes.
Fix ANOTHER prototype error.
Merge branch 'ncn-devel' into dinglist-cleanup

Conflicts:
	dataobj/dingliste.cc
Merge branch 'ncn-devel' into mail-revenue
Fix implementation of dingliste_t::suche to match new convention for meaning of capacity.
Improve function documentation in dingliste_t
Minor improvements to credit limit / insolvency messages.
Merge branch 'ncn-devel' into mail-revenue
Merge branch 'ncn-devel' into dinglist-cleanup

Conflicts:
	gui/money_frame.cc
Further instrumentation for debugging.
Add speed/time/distance conversion routines to simunits.h
Small comment improvement
Add passengers discarded due to waiting too long to the "too slow" graph, not the "unhappy" graph (which represents overcrowding)