CHANGE: Make the forcing of station coverage for factories to be at least 3 limited to saved games with the current, not next version.
CODE: Add debug messages for each modal dialogue for debugging purposes.
CODE: Downgrade the debug level of "duplicate hash", as this is not necessarily an error.
FIX: Compile error from previous commit.
FIX: Rounding error lead to crashes on a new month in some cases.
FIX: Crash on loading in some cases.
FIX: Possible fix for crashes on new month in the command line server.
REVERT: Previous attempted fix: this caused desyncs and did not fix the crash.

Signed-off-by: James E. Petts <jamespetts@yahoo.com>
FIX: Possible fixes for server crashes
CODE: Better casting
CODE: Rationalise calculation of vehicle resale value to remove floating point arithmeitc
Fix more save file load scenarios.
Fix subtle stupid bugs related to factory coverage.
Merge commit 'dce5fb9e0e' (Fixes from James's 11.x branch) into emergency-depot-bugfix
Fix the divide by zero error previously fixed by commit dc35fb9, but fix it better.
Merge commit 'e28358' (fixes from James's 11.x branch) into emergency-depot-bugfix
Fix floating point use in vehikel_t::calc_restwert() correctly (James's fix still had system floating point math hidden in it)
Fix silly const error from previous commit.
Fix problem with previous floating point fix -- now it should really use our float type
Merge branch 'emergency-depot-bugfix' of git://github.com/neroden/simutrans.git into 112.x-private-car-merge