acinclude & sdl2.m4 updates:

- acinclude/alsa.m4, esd.m4: Ran through autoupdate to replace several
  AC_TRY_[COMPILE|LINK|RUN] with corresponding AC_???_IFELSE , so that
  autoconf-2.70 doesn't warn.
- sdl2.m4: Ditto.
- test/acinclude.m4 (sdl2): Ditto.

acinclude/alsa.m4

@@ -72,11 +72,10 @@ no_alsa=""
     alsa_min_micro_version=`echo $min_alsa_version | \
            sed 's/\([[0-9]]*\).\([[0-9]]*\).\([[0-9]]*\)/\3/'`
 
-AC_LANG_SAVE
-AC_LANG_C
-AC_TRY_COMPILE([
+AC_LANG_PUSH([C])
+AC_COMPILE_IFELSE([AC_LANG_PROGRAM([[
 #include <alsa/asoundlib.h>
-], [
+]], [[
 /* ensure backward compatibility */
 #if !defined(SND_LIB_MAJOR) && defined(SOUNDLIB_VERSION_MAJOR)
 #define SND_LIB_MAJOR SOUNDLIB_VERSION_MAJOR
@@ -108,13 +107,13 @@ AC_TRY_COMPILE([
 #    endif
 #  endif
 exit(0);
-],
+]])],
   [AC_MSG_RESULT(found.)],
   [AC_MSG_RESULT(not present.)
    ifelse([$3], , [AC_MSG_ERROR(Sufficiently new version of libasound not found.)])
    alsa_found=no]
 )
-AC_LANG_RESTORE
+AC_LANG_POP([C])
 
 dnl Now that we know that we have the right version, let's see if we have the library and not just the headers.
 if test "x$enable_alsatest" = "xyes"; then