made aclocal/automake 1.8 a bit more happy

Imported-from: https://svn.code.sf.net/p/dosbox/code-0/dosbox/trunk@1889

acinclude.m4

@@ -1,7 +1,7 @@
 dnl AM_PATH_SDL([MINIMUM-VERSION, [ACTION-IF-FOUND [, ACTION-IF-NOT-FOUND]]])
 dnl Test for SDL, and define SDL_CFLAGS and SDL_LIBS
 dnl
-AC_DEFUN(AM_PATH_SDL,
+AC_DEFUN([AM_PATH_SDL],
 [dnl 
 dnl Get the cflags and libraries from the sdl-config script
 dnl
@@ -174,7 +174,7 @@ dnl
 dnl For backwards compatibility, if ACTION_IF_NOT_FOUND is not specified,
 dnl and the alsa libraries are not found, a fatal AC_MSG_ERROR() will result.
 dnl
-AC_DEFUN(AM_PATH_ALSA,
+AC_DEFUN([AM_PATH_ALSA],
 [dnl Save the original CFLAGS, LDFLAGS, and LIBS
 alsa_save_CFLAGS="$CFLAGS"
 alsa_save_LDFLAGS="$LDFLAGS"
@@ -376,4 +376,4 @@ typedef         double     Real64;
   typedef Bit64s Bits;
  #endif
 
-])
+])