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.

sdl2.m4

@@ -8,6 +8,7 @@
 # Changelog:
 # * also look for SDL2.framework under Mac OS X
 # * removed HP/UX 9 support.
+# * updated for newer autoconf.
 
 # serial 2
 
@@ -110,7 +111,7 @@ dnl Now check if the installed SDL is sufficiently new. (Also sanity
 dnl checks the results of sdl2-config to some extent
 dnl
       rm -f conf.sdltest
-      AC_TRY_RUN([
+      AC_RUN_IFELSE([AC_LANG_SOURCE([[
 #include <stdio.h>
 #include <stdlib.h>
 #include "SDL.h"
@@ -145,7 +146,7 @@ int main (int argc, char *argv[])
     }
 }
 
-],, no_sdl=yes,[echo $ac_n "cross compiling; assumed OK... $ac_c"])
+]])], [], [no_sdl=yes], [echo $ac_n "cross compiling; assumed OK... $ac_c"])
         CFLAGS="$ac_save_CFLAGS"
         CXXFLAGS="$ac_save_CXXFLAGS"
         LIBS="$ac_save_LIBS"
@@ -176,7 +177,7 @@ int main (int argc, char *argv[])
           CFLAGS="$CFLAGS $SDL_CFLAGS"
           CXXFLAGS="$CXXFLAGS $SDL_CFLAGS"
           LIBS="$LIBS $SDL_LIBS"
-          AC_TRY_LINK([
+          AC_LINK_IFELSE([AC_LANG_PROGRAM([[
 #include <stdio.h>
 #include "SDL.h"
 
@@ -184,7 +185,7 @@ int main(int argc, char *argv[])
 { return 0; }
 #undef  main
 #define main K_and_R_C_main
-],      [ return 0; ],
+]], [[ return 0; ]])],
         [ echo "*** The test program compiled, but did not run. This usually means"
           echo "*** that the run-time linker is not finding SDL or finding the wrong"
           echo "*** version of SDL. If it is not finding SDL, you'll need to set your"