* configure.in (M4): Check for m4, and m4 handling eight-bit quote

characters.

Rev: configure.in:1.39

configure.in

@@ -121,6 +121,10 @@ AC_PROG_MAKE_SET
 AC_PROG_RANLIB
 AM_PROG_CC_STDC
 
+if test x$am_cv_prog_cc_stdc = xno ; then
+  AC_ERROR([the C compiler doesn't handle ANSI-C])
+fi
+
 # Use a particular scheme implementation?
 if test x$with_scheme != x ; then
   AC_PATH_PROG(SCHEME_PROGRAM, $with_scheme,, $PATH)
@@ -138,9 +142,21 @@ AC_SUBST(SCHEME_NAME)
 
 AC_PATH_PROG(BASH, bash,, $PATH)
 AC_PATH_PROG(GROFF, groff,, $PATH)
-
-if test x$am_cv_prog_cc_stdc = xno ; then
-  AC_ERROR([the C compiler doesn't handle ANSI-C])
+AC_PATH_PROG(M4, m4, m4)
+
+AC_CACHE_CHECK([if m4 can handle eight-bit quote characters],
+  lsh_cv_prog_m4_quote_8bit,
+  [ if test xfoo = x`echo 'change''quote(,)foo' | $M4`; then
+      lsh_cv_prog_m4_quote_8bit=yes
+    else   
+      lsh_cv_prog_m4_quote_8bit=no
+    fi])
+
+if test x$lsh_cv_prog_m4_quote_8bit = xno; then
+  AC_MSG_WARN(  
+[Upgrade to a better version than GNU m4 1.4,
+or recompile it with CFLAGS=-funsigned-char.])
+  M4=false --
 fi
 
 dnl Checks for libraries.