Say malloc/realloc cache vars can have spaces

Author: eggert

Diff for: doc/autoconf.texi

@@ -5390,6 +5390,7 @@ rpl_malloc (size_t n)
 
 The result of this macro is cached in the
 @code{ac_cv_func_malloc_0_nonnull} variable.
+The result might contain spaces, e.g., @code{guessing yes}.
 
 If you don't want to maintain a @code{malloc.c} file in your package
 manually, you can instead use the Gnulib module @code{malloc-gnu}.
@@ -5497,6 +5498,7 @@ the native @code{realloc} is not used in the main project.  See
 
 The result of this macro is cached in the
 @code{ac_cv_func_realloc_0_nonnull} variable.
+The result might contain spaces, e.g., @code{guessing yes}.
 
 This macro does not check compatibility with glibc @code{realloc (@var{p}, 0)}
 when @var{p} is non-null, as glibc 1--2.1 behaves differently from glibc