Remove some ancient and unmaintained encoding-conversion test cruft.

In commit 9211919 I claimed that we weren't testing encoding
conversion functions, but further poking around reveals that we did
have an equivalent though hard-wired set of tests in conversion.sql.
AFAICS there is no advantage to doing it like that as compared to letting
the catalog contents drive the test, so let the opr_sanity addition stand
and remove the now-redundant tests in conversion.sql.

Also, remove some infrastructure in src/backend/utils/mb/conversion_procs
for building conversion.sql's list of tests.  That was unmaintained, and
had not corresponded to the actual contents of conversion.sql since 2007
or perhaps even further back.

Author: tglsfdc

src/backend/utils/mb/conversion_procs/Makefile

@@ -14,9 +14,6 @@ include $(top_builddir)/src/Makefile.global
 
 SQLSCRIPT = conversion_create.sql
 
-# This file can be placed as src/test/regress/sql/conversion.sql
-REGRESSION_SCRIPT = conversion.sql
-
 SUBDIRS = \
 	ascii_and_mic cyrillic_and_mic euc_cn_and_mic euc_jp_and_sjis \
 	euc_kr_and_mic euc_tw_and_big5 latin2_and_win1250 latin_and_mic \
@@ -184,23 +181,6 @@ $(SQLSCRIPT): Makefile
 		echo; \
 	done > $@
 
-$(REGRESSION_SCRIPT): Makefile
-	@set -e; \
-	cp regress_prolog $@; \
-	set $(CONVERSIONS) ; \
-	while [ "$$#" -gt 0 ] ; \
-	do \
-		name=$$1;shift; \
-		se=$$1;shift; \
-		de=$$1; shift; \
-		func=$$1; shift; \
-		obj=$$1; shift; \
-		echo "-- $$se --> $$de"; \
-		echo "SELECT CONVERT('foo' USING $$name);"; \
-		echo "SELECT CONVERT('foo', '$$se', '$$de');"; \
-	done >> $@; \
-	cat regress_epilogue >> $@;
-
 install: $(SQLSCRIPT) installdirs
 	$(INSTALL_DATA) $(SQLSCRIPT) '$(DESTDIR)$(datadir)'