Update configure.ac

* Use AS_HELP_STRING instead of deprecated AC_HELP_STRING
* Use AC_OUTPUT without arguments
* Enclose AC_INIT argument in brackets
* Add automake option std-options

(cherry picked from commit 53a33e1db2c9a58b867f7db26c5f476c3ee4b00b)

configure.ac

@@ -1,8 +1,8 @@
 
-AC_INIT(ncdu, 1.14.2, projects@yorhel.nl)
+AC_INIT([ncdu],[1.14.2],[projects@yorhel.nl])
 AC_CONFIG_SRCDIR([src/global.h])
 AC_CONFIG_HEADER([config.h])
-AM_INIT_AUTOMAKE([foreign subdir-objects])
+AM_INIT_AUTOMAKE([foreign std-options subdir-objects])
 
 # Check for programs.
 AC_PROG_CC
@@ -33,10 +33,10 @@ AC_CHECK_FUNCS(
 # Look for ncurses library to link to
 ncurses=auto
 AC_ARG_WITH([ncurses],
-            AC_HELP_STRING([--with-ncurses], [compile/link with ncurses library] ),
+            [AS_HELP_STRING([--with-ncurses], [compile/link with ncurses library] )],
             [ncurses=ncurses])
 AC_ARG_WITH([ncursesw],
-            AC_HELP_STRING([--with-ncursesw], [compile/link with wide-char ncurses library @<:@default@:>@]),
+            [AS_HELP_STRING([--with-ncursesw], [compile/link with wide-char ncurses library @<:@default@:>@])],
             [ncurses=ncursesw])
 if test "$ncurses" = "auto" -o "$ncurses" = "ncursesw"; then
   PKG_CHECK_MODULES([NCURSES], [ncursesw], [LIBS="$LIBS $NCURSES_LIBS"; ncurses=ncursesw],
@@ -65,4 +65,5 @@ AC_MSG_NOTICE([Using $DEFAULT_SHELL as the default shell if \$SHELL is not set])
 AC_DEFINE_UNQUOTED(DEFAULT_SHELL, "$DEFAULT_SHELL", [Used default shell interpreter])
 
 
-AC_OUTPUT([Makefile])
+AC_CONFIG_FILES([Makefile])
+AC_OUTPUT