Fix ./configure errors on newer autoconf.

Fixes #134.

configure.ac

@@ -14,10 +14,9 @@
 
 define([thisversion],[1.8.0])
 define([nextversion],[1.8.0])
-AC_INIT([xsecurelock],thisversion,[[email protected]])
+AC_INIT([xsecurelock],[thisversion],[[email protected]])
 AM_INIT_AUTOMAKE([-Wall subdir-objects foreign])
 AC_PROG_CC
-AC_PROG_CC_C99
 
 AC_DEFUN([RP_TRY_CC_FLAG], [
 	AC_MSG_CHECKING([whether the compiler supports $1])
@@ -43,14 +42,14 @@ AC_LINK_IFELSE([AC_LANG_PROGRAM([])],
                 LDFLAGS=$saved_LDFLAGS])
 
 AC_CHECK_HEADER(X11/Xlib.h,
-                [], [AC_ERROR([X includes not found.])])
+                [], [AC_MSG_ERROR(X includes not found.)])
 AC_CHECK_LIB(X11, XOpenDisplay,
-             [], [AC_ERROR([X library not found.])])
+             [], [AC_MSG_ERROR(X library not found.)])
 AC_CHECK_LIB(Xmuu, XmuClientWindow,
              [], [AC_CHECK_LIB(Xmu, XmuClientWindow,
-             [], [AC_ERROR([Xmuu or Xmu library not found.])])])
+             [], [AC_MSG_ERROR(Xmuu or Xmu library not found.)])])
 AC_CHECK_LIB(m, sqrt,
-             [], [AC_ERROR([Math library not found.])])
+             [], [AC_MSG_ERROR(Math library not found.)])
 
 # RP_SEARCH_LIBS(sym, lib, macro, flag, default, description)
 AC_DEFUN([RP_SEARCH_LIBS], [
@@ -206,7 +205,7 @@ enable_pam_check_account_type=no
 
 AS_IF([test x$have_pam = xtrue], [
   AC_ARG_WITH([pam_service_name],
-              AC_HELP_STRING([--with-pam-service-name],
+              AS_HELP_STRING([--with-pam-service-name],
                              [The name of the PAM service that xsecurelock's
                               auth helpers will authenticate as by default.
                               This flag is mandatory. Be sure to verify that
@@ -218,7 +217,7 @@ AS_IF([test x$have_pam = xtrue], [
         [AC_MSG_WARN([/etc/pam.d/$pam_service_name doesn't exist. Sure?])])
 
   AC_ARG_ENABLE([pam_check_account_type],
-                AC_HELP_STRING([--enable-pam-check-account-type],
+                AS_HELP_STRING([--enable-pam-check-account-type],
                                [Enable checking of PAM accounting result. Only
                                 enable this if accounting is properly configured
                                 on your system; especially keep this disabled if
@@ -230,7 +229,7 @@ AS_IF([test x$have_pam = xtrue], [
 ])
 
 AC_ARG_WITH([default_auth_module],
-            AC_HELP_STRING([--with-default-auth-module],
+            AS_HELP_STRING([--with-default-auth-module],
                            [The default authentication module to use when none
                             was specified. Can be overridden via the
                             XSECURELOCK_AUTH environment variable or a command
@@ -241,7 +240,7 @@ AC_ARG_WITH([default_auth_module],
 AC_MSG_NOTICE([Configured default auth module: $auth_executable])
 
 AC_ARG_WITH([default_authproto_module],
-            AC_HELP_STRING([--with-default-authproto-module],
+            AS_HELP_STRING([--with-default-authproto-module],
                            [The default authentication protocol module to use when none was
                             specified. Can be overridden via the
                             XSECURELOCK_AUTHPROTO environment variable. By
@@ -263,7 +262,7 @@ AC_ARG_WITH([default_authproto_module],
 AC_MSG_NOTICE([Configured default authproto module: $authproto_executable])
 
 AC_ARG_WITH([default_global_saver_module],
-            AC_HELP_STRING([--with-default-global-saver-module],
+            AS_HELP_STRING([--with-default-global-saver-module],
                            [The default global saver module to use when none was
                             specified. Can be overridden via the
                             XSECURELOCK_GLOBAL_SAVER environment variable.]),
@@ -274,7 +273,7 @@ AC_MSG_NOTICE([Configured default global saver module: ]dnl
 [$global_saver_executable])
 
 AC_ARG_WITH([default_saver_module],
-            AC_HELP_STRING([--with-default-saver-module],
+            AS_HELP_STRING([--with-default-saver-module],
                            [The default per-screen saver module to use when none
                             was specified. Can be overridden via the
                             XSECURELOCK_SAVER environment variable.]),