Distinguish the stable from the beta builds.
installer: add the "Beta" suffix in FullAppNameVer and simplify the preprocessor checks
installer: include the rev number and hash only for beta releases
version.h: break the defines and reindent the file for better readability
AboutDlg.cpp: use the MPC_VERSION_ARCH define
build.bat: Add the Beta suffix for beta builds and drop revision number for stable builds.
installer: minor simplification
vsfilter_setup.iss: add the Beta suffix for beta builds.