Produce HISTORY file consistently as ASCII

The release notes may contain non-ASCII characters (for contributor
names), which lynx converts to the encoding determined by the current
locale.  The get output that is deterministic and easily readable by
everyone, we make lynx produce LATIN1 and then convert that to ASCII
with transliteration for the non-ASCII characters.

doc/src/sgml/Makefile

@@ -206,10 +206,19 @@ postgres.pdf:
 ##
 
 JADE.text = $(JADE) $(JADEFLAGS) $(SGMLINCLUDE) $(CATALOG) -d stylesheet.dsl -i output-text -t sgml
+ICONV = iconv
 LYNX = lynx
 
+# The release notes may contain non-ASCII characters (for contributor
+# names), which lynx converts to the encoding determined by the
+# current locale.  The get output that is deterministic and easily
+# readable by everyone, we make lynx produce LATIN1 and then convert
+# that to ASCII with transliteration for the non-ASCII characters.
+# Official releases are currently built on FreeBSD, which has limited
+# locale support and is very picky about locale name spelling.  The
+# below has been finely tuned to run on FreeBSD and Linux/glibc.
 INSTALL HISTORY regress_README: % : %.html
-	$(PERL) -p -e 's/<H(1|2)$$/<H\1 align=center/g' $< | $(LYNX) -force_html -dump -nolist -stdin > $@
+	$(PERL) -p -e 's/<H(1|2)$$/<H\1 align=center/g' $< | LC_ALL=en_US.ISO8859-1 $(LYNX) -force_html -dump -nolist -stdin | $(ICONV) -f latin1 -t us-ascii//TRANSLIT > $@
 
 INSTALL.html: standalone-install.sgml installation.sgml version.sgml
 	$(JADE.text) -V nochunks standalone-install.sgml installation.sgml > $@