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

@@ -226,7 +226,7 @@ set(CORRADE_CMAKE_MODULE_INSTALL_DIR ${CORRADE_INCLUDE_INSTALL_PREFIX}/share/cma
 set(CORRADE_INCLUDE_INSTALL_DIR ${CORRADE_INCLUDE_INSTALL_PREFIX}/include/Corrade)
 
 # Library version
-set(CORRADE_LIBRARY_VERSION 2.0)
+set(CORRADE_LIBRARY_VERSION 2.1)
 set(CORRADE_LIBRARY_SOVERSION 2)
 
 add_subdirectory(modules)