Add postfix version number to identify beta (and other) versions.
Fix handling of credits.cpp and thus allow completely out-of-source builds.

credits.cpp now is not generated in the src/ directory anymore,
but in your build directory (where it should be).
Try searching for CEGUI 0.7.x first before downloading and compiling it.

Some distributions still provide the old CEGUI.
Merge branch 'release-2.0.0' of https://github.com/Secretchronicles/SMC into release2Dot0SaveGameFixes