Dup frames shouldn't adapt.

Adapting during a dup frame caused jittery network performance
(especially when using high dup values).
The demoplayback check also didn't need to be there anyway.
Merge branch 'master' of https://github.com/rheit/zdoom
Fixed: No sprites were loaded for Build maps
Move SpriteFrames.Clear() from R_InitSprites to FTextureManager::Init

- Fixed: Blood sprite rotations were overwritten by the Doom sprite
  rotations.
Don't reopen the reader for encrypted maps

- Fixed: Memory leak when loading Blood maps.
Never cache nodes for Build maps
Fix typo in comment
Fixed: None of the Blood ambient sounds were registered correctly
Correctly assign the sample rate for all Blood SFX formats

- Blood can do 44100 Hz sounds!
Use Blood player starts

- Blood's maps use thing types, much like Doom's, so getting its player
  starts is easy. There's no need to synthesize a start from the editor
  position like with other Build maps.
Don't weed out wall and floor sprites when spawning Build sprites
Remove slopetype from line_t.

- Recomputing it in the only two places where it's used is trivial, so
  it's basically a waste of space to precompute it.
Remove polymost stuff

- Maybe it will be back someday, but it's been essentially dead for nearly
  10 years, so don't hold your breath.
Consolidate wall texturing vars into two structs

- All transformation and clipping values go into FWallCoords.
- All texture mapping values go into FWallTMapVals.
Pass WallC as a parameter to (O)WallMost instead of referencing it globally
Pass x1 and x2 to Prep(L)Wall as params
Consolidate some common code for texture mapping setup

- R_AddLine() and R_RenderDecal() had nearly identical code for setting up
  texture mapping. These have now been spun off into methods of
  FWallCoords and FWallTmapVals.
Set face/wall/floor flags from Build sprites
Add CVar for drawing weapons in the althud
Fixed build on compilers other than MSVC

No more "Call to 'LittleShort' is ambiguous" error