Ignore the minor version number when checking for DRO v1 files

- There exist files where the first word of the version number for DRO v1
  files is not 0 but something else completely. (Maybe it's not actually a
  version number?) Assume they are valid v1 files as long as the second
  word is a 1.
Fixed: userinfo_t::SkinChanged() was unaware of player classes
Delay skin setting on save load until player class is known.

- Fixed: Loading players from savegames set the skin before their current
  class was retrieved, so they could not validate their skins with the
  correct class.
Add NoPushWindowCheck compatibility flag

- For maps like xtheateriii that expect non-blocking push lines to
  activate when you are standing on them and run into a completely different
  line, there is now this compatiblity.txt-only flag.
Clamp xy angle range in P_SetSlope()

- This function just assumed that every xy angle passed to it was within
  the range [0,360). This is obviously bad, since anything outside that
  range can result in accessing data outside the range of the finecosine
  and finesine tables.
Don't free replaced textures that are used as patches.

- Fixed: If a part of a multipatch texture is replaced by a HIRESTEX
  version, the original patch must not be deleted, since the multipatch
  texture still needs it for compositing.
Merge branch 'maint'