eu07 reads static terrain from files named by "terrain ... endterrain":
text (.txtf) or its binary version (.btf). The scenery check now tells a
terrain file of which neither is there (MissingTerrainFile).
Such a file also takes the place of the scenery's .sbt, so the terrain
includes after it are read after all and a missing one is told again. When
the .sbt was already used before the directive - a terrain include or
terrain geometry passed over, or FirstInit - the simulator passes the file
over instead, which is told too (TerrainFileBehindSbt). The parser takes
the lookup of files and whether there is an .sbt as one SceneryFileLookup.
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