po: Use more standard names for the Serbian locales.
diff --git a/configure b/configure
index d5de334..115cf84 100755
--- a/configure
+++ b/configure
@@ -15431,8 +15431,8 @@
 ru \
 sk \
 sl \
-sr_Latn_SP \
-sr_SP \
+sr_RS@cyrillic \
+sr_RS@latin \
 sv \
 te \
 th \