Wrong parsing of backslash inside backquote

[schwab]

Configuration Information [Automatically generated, do not change]:
Machine: ia64
OS: linux
Compiler: gcc -I/usr/src/packages/BUILD/bash-3.1 
-L/usr/src/packages/BUILD/bash-3.1/../readline-5.1
Compilation CFLAGS:  -DPROGRAM='bash' -DCONF_HOSTTYPE='ia64' 
-DCONF_OSTYPE='linux' -DCONF_MACHTYPE='ia64-suse-linux' -DCONF_VENDOR='suse' 
-DLOCALEDIR='/usr/share/locale' -DPACKAGE='bash' -DSHELL -DHAVE_CONFIG_H   -I.  
-I. -I./include -I./lib   -O2 -fmessage-length=0 -Wall -D_FORTIFY_SOURCE=2 -g 
-D_GNU_SOURCE -DRECYCLES_PIDS -Wall -pipe -g -fbranch-probabilities
uname output: Linux sykes 2.6.16-rc5-git9-2-default #1 SMP Tue Mar 7 14:56:34 
UTC 2006 ia64 ia64 ia64 GNU/Linux
Machine Type: ia64-suse-linux

Bash Version: 3.1
Patch Level: 11
Release Status: release

Description:
        A backslash inside `...` leads to a parse error when it is the
        last character in a single quoted string.

Repeat-By:
        $ cat x.sh
        foo `bar 'a\'`
        $ sh x.sh
        x.sh: line 1: unexpected EOF while looking for matching `''
        x.sh: line 2: syntax error: unexpected end of file