Bump the soversion for 2018.10.

Unlike in 2018.04 there were no extremely breaking changes, so not
bumping the major version.

Author: mosra

CMakeLists.txt

@@ -373,7 +373,7 @@ set(MAGNUM_PLUGINS_AUDIOIMPORTER_DEBUG_DIR ${MAGNUM_PLUGINS_DEBUG_DIR}/audioimpo
 set(MAGNUM_PLUGINS_AUDIOIMPORTER_RELEASE_DIR ${MAGNUM_PLUGINS_RELEASE_DIR}/audioimporters)
 
 # Library version
-set(MAGNUM_LIBRARY_VERSION 2.0)
+set(MAGNUM_LIBRARY_VERSION 2.1)
 set(MAGNUM_LIBRARY_SOVERSION 2)
 
 add_subdirectory(modules)