Add --disable-xmlto configure option

Added the check of xmlto program in configure script.
Also added --disable-xmlto configure option for systems with a broken
or older xmlto that doesn't work properly.

Signed-off-by: Takashi Iwai <tiwai@suse.de>

alsactl/Makefile.am

@@ -1,7 +1,10 @@
 SUBDIRS = init
 
 sbin_PROGRAMS=alsactl
-man_MANS=alsactl.1 alsactl_init.7
+man_MANS=alsactl.1
+if USE_XMLTO
+man_MANS += alsactl_init.7
+endif
 EXTRA_DIST=alsactl.1 alsactl_init.xml
 
 alsactl_SOURCES=alsactl.c state.c utils.c init_parse.c

configure.in

@@ -52,6 +52,17 @@ AC_ARG_ENABLE(alsaconf,
      esac],[alsaconf=true])
 AM_CONDITIONAL(ALSACONF, test x$alsaconf = xtrue)
 
+xmlto=""
+if test x"$alsaconf" = xtrue; then
+   AC_ARG_ENABLE(xmlto,
+     AS_HELP_STRING([--disable-xmlto], [Disable man page creation via xmlto]),
+     xmlto="$enableval", xmlto="yes")
+   if test "$xmlto" = "yes"; then
+      AC_CHECK_PROG([xmlto], [xmlto], [yes])
+   fi
+fi
+AM_CONDITIONAL(USE_XMLTO, test x"$xmlto" = xyes)
+
 dnl Checks for header files.
 AC_HEADER_STDC
 if test x$alsamixer = xtrue; then