Add regression test files inadvertantly omitted in plperl.on_plperl{u}_init patch

src/pl/plperl/sql/plperl_init.sql

@@ -0,0 +1,10 @@
+-- test plperl.on_plperl_init errors are fatal
+
+-- Avoid need for custom_variable_classes = 'plperl'
+LOAD 'plperl';
+
+SET SESSION plperl.on_plperl_init = ' eval "1+1" ';
+
+SHOW plperl.on_plperl_init;
+
+DO $$ warn 42 $$ language plperl;