Increment libavrdude version

There is bound to be a library change in git main until v8.1 is published;
ensure we have a new version number in preparation for the next release.

Author: stefanrueger

src/CMakeLists.txt

@@ -308,8 +308,8 @@ add_library(libavrdude
 set_target_properties(libavrdude PROPERTIES
     PREFIX ""
     PUBLIC_HEADER "libavrdude.h;libavrdude-avrintel.h"
-    VERSION 2.0.0
-    SOVERSION 2
+    VERSION 3.0.0
+    SOVERSION 3
     )
 
 target_include_directories(libavrdude