Fix version number.
https://github.com/irstlm-team/irstlm/issues/25
--- CMakeLists.txt.orig	2015-12-09 17:31:15.000000000 -0600
+++ CMakeLists.txt	2023-02-05 21:09:06.000000000 -0600
@@ -5,5 +5,5 @@
 
-SET(IRSTLM_VERSION_MAJOR "5")
-SET(IRSTLM_VERSION_MINOR "80")
-SET(IRSTLM_VERSION_PATCH "08")
+SET(IRSTLM_VERSION_MAJOR "6")
+SET(IRSTLM_VERSION_MINOR "00")
+SET(IRSTLM_VERSION_PATCH "05")