-fixed the file validity checks in MapData::GetChecksum.

They need to be done per lump, because MapData::Seek can alter the FileReader being used for a specific lump. Even worse, the FileReader will be NULL when the function as it was is called for a map inside a Zip-file.
Merge branch 'master' of https://github.com/rheit/zdoom
- fixed: The crosshair setting code checked for existence of lumps, not textures and missed anything defined in a TEXTURES lump.
- fixed: G_FinishTravel must clear the MF2_BLASTED flag off the player pawn because this flag will result in damage from contact with other objects in the map.
- fixed: When validating the crouch sprite it was assumed that both the regular and the crouch sprite were having full rotations.
- fixed: A_CustomMissile should not jump to the See state for dead monsters when using CMF_CHECKTARGETDEAD.
- fixed: In Raven games, don't chase after monsters in the titlemap or when actor has a goal.
- fixed: G_ChangeLevel must resolve warptrans map links before getting the next level's levelinfo.
- remove debug stuff.
- fixed: When a sprite is being renamed by Dehacked it also needs to be changed in the list of original sprite names, otherwise any subsequent attempt to use the altered sprite in a frame definition will fail.
- added a compatibility option for Hexen's MAP04 to change the z-position of 4 quartz flasks that get lowered into a pool of lava but were incorrectly positioned 48 map units above the floor.
- use a separate counter from AActor::special1 to count weapon use with some Hexen weapons. special1 is used for some other purposes as well, and when using a separate counter it can be reset to 0 when changing weapons, preventing counting errors.
Merge branch 'master' of https://github.com/rheit/zdoom into z_osx_clean