Fix build with postgresql 10.

Sponsored by:	Absolight

databases/postgresql-plruby/files/patch-extconf.rb

@@ -0,0 +1,11 @@
+--- extconf.rb.orig	2017-08-31 10:56:23 UTC
++++ extconf.rb
+@@ -122,6 +122,8 @@ end
+ case version_str = `#{pg_config} --version`
+ when /^PostgreSQL ([7-9])\.([0-9]{1,3})(\.[0-9]{1,3})?$/
+    version = 10 * $1.to_i + $2.to_i
++when /^PostgreSQL 10/
++   version = 100
+ else
+    version = 0
+ end