Bump to soversion=19, 1.8.3

Note that cmake is deprecated, but we keep it in-sync manually for now.
diff --git a/meson.build b/meson.build
index 010e06b..f2a6800 100644
--- a/meson.build
+++ b/meson.build
@@ -1,7 +1,7 @@
 project(
   'jsoncpp',
   'cpp',
-  version : '1.8.2',
+  version : '1.8.3',
   default_options : [
     'buildtype=release',
     'warning_level=1'],
@@ -52,7 +52,7 @@
     'src/lib_json/json_reader.cpp',
     'src/lib_json/json_value.cpp',
     'src/lib_json/json_writer.cpp'],
-  soversion : 18,
+  soversion : 19,
   install : true,
   include_directories : jsoncpp_include_directories)