Add make rules to download raw Unicode mapping files

This serves as implicit documentation and is handy if someone wants to
tweak things.  The rules are not part of a normal build, like this
entire directory.

src/backend/utils/mb/Unicode/Makefile

@@ -108,3 +108,37 @@ distclean: clean
 
 maintainer-clean: distclean
 	rm -f $(MAPS)
+
+
+DOWNLOAD = wget -O $@ --no-use-server-timestamps
+#DOWNLOAD = curl -o $@
+
+BIG5.TXT CNS11643.TXT:
+	$(DOWNLOAD) http://ftp.unicode.org/Public/MAPPINGS/OBSOLETE/EASTASIA/OTHER/$(@F)
+
+euc-jis-2004-std.txt sjis-0213-2004-std.txt:
+	$(DOWNLOAD) http://x0213.org/codetable/$(@F)
+
+gb-18030-2000.xml:
+	$(DOWNLOAD) https://ssl.icu-project.org/repos/icu/data/trunk/charset/data/xml/$(@F)
+
+GB2312.TXT:
+	$(DOWNLOAD) 'http://trac.greenstone.org/browser/trunk/gsdl/unicode/MAPPINGS/EASTASIA/GB/GB2312.TXT?rev=1842&format=txt'
+
+JIS0201.TXT JIS0208.TXT JIS0212.TXT:
+	$(DOWNLOAD) http://ftp.unicode.org/Public/MAPPINGS/OBSOLETE/EASTASIA/JIS/$(@F)
+
+JOHAB.TXT KSX1001.TXT:
+	$(DOWNLOAD) http://ftp.unicode.org/Public/MAPPINGS/OBSOLETE/EASTASIA/KSC/$(@F)
+
+KOI8-R.TXT KOI8-U.TXT:
+	$(DOWNLOAD) http://ftp.unicode.org/Public/MAPPINGS/VENDORS/MISC/$(@F)
+
+$(ISO8859TEXTS):
+	$(DOWNLOAD) http://ftp.unicode.org/Public/MAPPINGS/ISO8859/$(@F)
+
+$(filter-out CP8%,$(WINTEXTS)):
+	$(DOWNLOAD) http://ftp.unicode.org/Public/MAPPINGS/VENDORS/MICSFT/WINDOWS/$(@F)
+
+$(filter CP8%,$(WINTEXTS)):
+	$(DOWNLOAD) http://ftp.unicode.org/Public/MAPPINGS/VENDORS/MICSFT/PC/$(@F)