bash asan fixes; minor documentation updates

lib/readline/doc/rluser.texi

@@ -1864,9 +1864,11 @@ pathname expansion.
 Display version information about the current instance of Bash.
 
 @item shell-expand-line (M-C-e)
-Expand the line as the shell does.
-This performs alias and history expansion as well as all of the shell
-word expansions (@pxref{Shell Expansions}).
+Expand the line by performing shell word expansions.  
+This performs alias and history expansion,
+$'@var{string}' and $"@var{string}" quoting,
+tilde expansion, parameter and variable expansion, arithmetic expansion,  
+word splitting, and quote removal.  
 
 @item history-expand-line (M-^)
 Perform history expansion on the current line.

lib/sh/shquote.c

@@ -188,7 +188,7 @@ sh_mkdoublequoted (const char *s, size_t slen, int flags)
 
   send = s + slen;
   mb_cur_max = flags ? MB_CUR_MAX : 1;
-  rlen = (flags == 0) ? slen + 3 : (2 * slen) + 1;
+  rlen = (flags == 0) ? slen + 3 : (2 * slen) + 3;
   ret = r = (char *)xmalloc (rlen);
 
   *r++ = '"';