back quotes and double quotes must not be escaped?

[Lars Hecking]

 Since upgrading from autoconf 2.54 to 2.54b, automake 1.7.1 gives me tons
 of warnings:

configure.ac:27: warning: back quotes and double quotes must not be escaped in: 
$as_me:$LINENO: WARNING: \`$CC' requires \`$lt_cv_prog_cc_shlib' to build 
shared libraries
configure.ac:27: warning: back quotes and double quotes must not be escaped in: 
$as_me: WARNING: \`$CC' requires \`$lt_cv_prog_cc_shlib' to build shared 
libraries
configure.ac:27: warning: back quotes and double quotes must not be escaped in: 
$as_me:$LINENO: WARNING: add \`$lt_cv_prog_cc_shlib' to the CC or CFLAGS env 
variable and reconfigure

 This is configure.ac line 27:

AC_PROG_LIBTOOL

 What's the problem? libtool is version 1.4.3.