Add STRESSAPPTEST_CPU_AARCH64 defintion for aarch64 CPU

This patch adds a new macro, STRESSAPPTEST_CPU_AARCH64, for aarch64 CPUs.
The file stressapptest_config.h.in is also refreshed using autoheader.

Signed-off-by: Wei Huang <wei@redhat.com>
diff --git a/configure b/configure
index 97d2c38..985b54c 100755
--- a/configure
+++ b/configure
@@ -2460,9 +2460,15 @@
 $as_echo "#define STRESSAPPTEST_CPU_ARMV7A /**/" >>confdefs.h
 
      ;; #(
+  *aarch64*) :
+
+
+$as_echo "#define STRESSAPPTEST_CPU_AARCH64 /**/" >>confdefs.h
+
+     ;; #(
   *) :
-    { $as_echo "$as_me:${as_lineno-$LINENO}: WARNING: Unsupported CPU: $host_cpu! Try x86_64, i686, powerpc, or armv7a" >&5
-$as_echo "$as_me: WARNING: Unsupported CPU: $host_cpu! Try x86_64, i686, powerpc, or armv7a" >&2;}
+    { $as_echo "$as_me:${as_lineno-$LINENO}: WARNING: Unsupported CPU: $host_cpu! Try x86_64, i686, powerpc, armv7a, or aarch64" >&5
+$as_echo "$as_me: WARNING: Unsupported CPU: $host_cpu! Try x86_64, i686, powerpc, armv7a, or aarch64" >&2;}
  ;;
 esac