Bump soversion to 24 (#1167)

diff --git a/meson.build b/meson.build
index 975d56c..75ec974 100644
--- a/meson.build
+++ b/meson.build
@@ -50,7 +50,7 @@
     'src/lib_json/json_value.cpp',
     'src/lib_json/json_writer.cpp',
   ]),
-  soversion : 23,
+  soversion : 24,
   install : true,
   include_directories : jsoncpp_include_directories,
   cpp_args: dll_export_flag)