(svn r10274) [0.5] -Backport from trunk (r9961, r10023, r10028, r10030, r10038, r10147):

- Fix: Some bits were unset when loading old TTD savegames when they shouldn't be unset (r10147)
- Fix: Sprite resulting from '?' substitution was reloaded into the cache entry for SPR_IMG_QUERY instead of the original sprite cache entry. This resulted in unaccounted missing sprite cache memory, and was exacerbated because the original missing sprite was not cached, so it did it again and again and again. Slowdowns and boom (r10038)
- Fix: One could build on (some) slopes when building on slopes was disabled [FS#823] (r10030)
- Fix: When deleting the first engine of a train with multiple engines, only reopen the train window if the player had the original train window open. This fixes 'random' windows opening for multiple players of the same company (r10028)
- Fix: When selling trains, if there were no wagons between multiheaded engines the rear part could be checked despite having already been deleted (10023)
- Fix: Some files were still in iso8859-15 instead of UTF-8 (r9961)

table/sprites.h

@@ -25,7 +25,7 @@
  * All sprites which are described here are referenced only one to a handful of times
  * throughout the code. When introducing new sprite enums, use meaningful names.
  * Don't be lazy and typing, and only use abbrevations when their meaning is clear or
- * the length of the enum would get out of hand. In that case EXPLAIN THE ABBREVATION
+ * the length of the enum would get out of hand. In that case EXPLAIN THE ABBREVATION
  * IN THIS FILE, and perhaps add some comments in the code where it is used.
  * Now, don't whine about this being too much typing work if the enums are like
  * 30 characters in length. If your editor doen't help you simplifying your work,