Bug #602744: Fix broken tip_of_the_day list creation.

Patch in r18417 from bug #602062 was buggy - removing the "-x c" argument.

git-svn-id: svn+ssh://svn.gnucash.org/repo/gnucash/trunk@18438 57a11ea4-9604-0410-9ed3-97b8803252fd

doc/Makefile.am

@@ -62,7 +62,7 @@ gnucash.1: gnucash.1.in Makefile
 	mv $@.tmp $@
 
 tip_of_the_day.list: tip_of_the_day.list.in Makefile
-	${CC} -E -P -D'N_(x)=x' -o $@.tmp $<
+	${CC} -E -P -x c -D'N_(x)=x' -o $@.tmp $<
 	cat -s $@.tmp | ${SED} -e 's/^ *\"\(.*\)\" *$$/\1/' > $@
 	rm -f $@.tmp