This check in updates SDL_atomic.h to reflect the new set of atomic operations in 32 and 64 bit form.

It also update configure.in to compile the linux version of the library. The three versions are all dummies
implementations that do nothing. They are being checked in as place holders. Mostly, I just wanted to get
place holders and the configure.in checked in.

--HG--
extra : convert_revision : svn%3Ac70aab31-4412-0410-b14c-859654838e24/trunk%403667

configure.in

@@ -217,6 +217,12 @@ SOURCES="$SOURCES $srcdir/src/video/*.c"
 
 dnl Enable/disable various subsystems of the SDL library
 
+AC_ARG_ENABLE(atomic,
+AC_HELP_STRING([--enable-atomic], [Enable the atomic operations subsystem [[default=yes]]]),
+              , enable_atomic=yes)
+if test x$enable_atomic != xyes; then
+    AC_DEFINE(SDL_ATOMIC_DISABLED)
+fi
 AC_ARG_ENABLE(audio,
 AC_HELP_STRING([--enable-audio], [Enable the audio subsystem [[default=yes]]]),
               , enable_audio=yes)
@@ -2433,6 +2439,16 @@ case "$host" in
             ;;
           esac
         fi
+        # Set up files for the atomic operations library
+        if test x$enable_atomic = xyes; then
+          case $ARCH in
+            linux)
+                AC_DEFINE(SDL_ATOMIC_LINUX)
+                SOURCES="$SOURCES $srcdir/src/atomic/linux/*.c"
+                have_atomic=yes
+            ;;
+          esac
+        fi
         # Set up files for the joystick library
         if test x$enable_joystick = xyes; then
           case $ARCH in