Update CMakeLists.txt

Author: simongog

lib/CMakeLists.txt

@@ -17,10 +17,12 @@ install(TARGETS sdsl
         RUNTIME DESTINATION bin
         LIBRARY DESTINATION lib
         ARCHIVE DESTINATION lib)
+        
+math(EXPR SOVERSION "${LIBRARY_VERSION_MAJOR}+1")
 
 set_target_properties(sdsl PROPERTIES
         VERSION "${LIBRARY_VERSION_FULL}"
-        SOVERSION "${LIBRARY_VERSION_MAJOR}"
+        SOVERSION "${SOVERSION}"
         #	DEFINE_SYMBOL SDSL_BUILD_DLL
         #	RUNTIME_OUTPUT_DIRECTORY "${CMAKE_CURRENT_BINARY_DIR}/../examples"
-        )
+)