Include the contents of PROJECT_DESCRIPTION in the PACKAGE_PREFIX.

If it's defined. PACKAGE_PREFIX is used to name tarballs and set their
base directory. The translation project has requested that we name
freeze-string traballs with a pre1 suffix; this makes that possible.

CMakeLists.txt

@@ -818,6 +818,9 @@ dist_add_generated (${BUILDING_FROM_VCS} ChangeLog)
 ############################ BEGIN MAKE DIST #################
 
 set(PACKAGE_PREFIX "${PROJECT_NAME}-${PROJECT_VERSION}")
+if (PROJECT_DESCRIPTION)
+  string(APPEND PACKAGE_PREFIX "-${PROJECT_DESCRIPTION}")
+endif()
 set(DIST_FILE "${PACKAGE_PREFIX}.tar")
 
 set(toplvl_DIST_local ${gnucash_DOCS}