rnd-20100521-2-src

rnd-20100521-2-src
* fixed problem with scrolling in native EM engine in multi-user mode
  (this bug was just introduced with the experimental viewport stuff)
* fixed animation of splashing acid in EM engine with classic artwork
* fixed animation of cracking nut in EM engine with classic artwork
* fixed (implemented) single step mode in native EM and SP engines
* fixed "latest_engine" flag in classic levels (moved to single sets)
* updated SDL library DLLs for Windows to the latest release versions
* replaced EM and SP set in classic level set with native level files
* finally added a newly written "CREDITS" file to the game package
* removed sampled music loops from classic music set