add the obelisk library source

src/meson.build

@@ -1,5 +1,6 @@
 conf_data = configuration_data()
 conf_data.set('version', meson.project_version())
+conf_data.set('so_version', project_version_lib)
 configure_file(input : 'version.h.in',
     output : 'version.h',
     configuration : conf_data

src/version.h.in

@@ -1,8 +0,0 @@
-namespace obelisk
-{
-    /**
-     * @brief The current version of obelisk.
-     *
-     */
-    std::string version = "@version@";
-} // namespace obelisk

src/version.h.in

@@ -0,0 +1 @@
+../include/version.h.in