[PATCH] Fix an infinitely recursing example

The "single" macro infinitely recurses because its expansion contains
the unquoted text " single-". The "double" macro almost has the same
problem, but it is protected by extra quotes. In any case, the macro
names being repeated in the macro definitions is not necessary.

This commit changes the macro names to "foo" and "bar", which are taken
from a very similar example in the GNU M4 1.4.17 manual. See lines 1971
to 1980 of v1.4.17:doc/m4.texi in the GNU M4 Git repository.
---
 doc/autoconf.texi | 8 ++++----
 1 file changed, 4 insertions(+), 4 deletions(-)

diff --git a/doc/autoconf.texi b/doc/autoconf.texi
index 4be1f70..9b7468b 100644
--- a/doc/autoconf.texi
+++ b/doc/autoconf.texi
@@ -10573,13 +10573,13 @@ quoting; if the usage is already inside a double-quoted string, then
 split it into concatenated strings.
 
 @example
-define([single], [a single-quoted $[]1 definition])
+define([foo], [a single-quoted $[]1 definition])
 @result{}
-define([double], [[a double-quoted $][1 definition]])
+define([bar], [[a double-quoted $][1 definition]])
 @result{}
-single
+foo
 @result{}a single-quoted $1 definition
-double
+bar
 @result{}a double-quoted $1 definition
 @end example
 
-- 
2.8.3