Encoding PG_UHC is code page 949.

This fixes presentation of non-ASCII messages to the Windows event log
and console in rare cases involving Korean locale.  Processes like the
postmaster and checkpointer, but not processes attached to databases,
were affected.  Back-patch to 9.4, where MessageEncoding was introduced.
The problem exists in all supported versions, but this change has no
effect in the absence of the code recognizing PG_UHC MessageEncoding.

Noticed while investigating bug #13427 from Dmitri Bourlatchkov.

src/backend/utils/mb/encnames.c

@@ -344,7 +344,7 @@ const pg_enc2name pg_enc2name_tbl[] =
 	DEF_ENC2NAME(SJIS, 932),
 	DEF_ENC2NAME(BIG5, 950),
 	DEF_ENC2NAME(GBK, 936),
-	DEF_ENC2NAME(UHC, 0),
+	DEF_ENC2NAME(UHC, 949),
 	DEF_ENC2NAME(GB18030, 54936),
 	DEF_ENC2NAME(JOHAB, 0),
 	DEF_ENC2NAME(SHIFT_JIS_2004, 932)