Modernize the autotools build system.

configure.ac

@@ -1,12 +1,24 @@
+# Initialize autoconf.
+AC_PREREQ([2.60])
 AC_INIT([libdivecomputer], [0.1])
+AC_CONFIG_SRCDIR([config.h.in])
+AC_CONFIG_HEADERS([config.h])
+
+# Initialize automake.
 AM_INIT_AUTOMAKE([-Wall -Werror foreign])
+
+# Initialize libtool.
+LT_PREREQ([2.2.0])
+LT_INIT([win32-dll])
+
+# Checks for programs.
 AC_PROG_CC
 AC_PROG_CC_C99
-AC_LIBTOOL_WIN32_DLL
-AC_PROG_LIBTOOL
 
+# Enable automake silent build rules.
 m4_ifdef([AM_SILENT_RULES],[AM_SILENT_RULES([yes])])
 
+# Checks for native Windows.
 AC_MSG_CHECKING([for native Win32])
 case "$host" in
   *-*-mingw*)
@@ -19,6 +31,7 @@ esac
 AC_MSG_RESULT([$os_win32])
 AM_CONDITIONAL([OS_WIN32], [test "$os_win32" = "yes"])
 
+# Checks for IrDA support.
 AC_CHECK_HEADERS([winsock2.h af_irda.h], [irda_win32=yes], [irda_win32=no], [
 #if HAVE_WINSOCK2_H
 #   include <winsock2.h>
@@ -39,7 +52,6 @@ AM_CONDITIONAL([IRDA], [test "$irda_win32" = "yes" || test "$irda_linux" = "yes"
 # Checks for library functions.
 AC_CHECK_FUNCS([localtime_r gmtime_r])
 
-AC_CONFIG_HEADERS([config.h])
 AC_CONFIG_FILES([
    libdivecomputer.pc
    Makefile