ARM: add some assembler convenience macros

Originally committed as revision 15724 to svn://svn.ffmpeg.org/ffmpeg/trunk

libavcodec/armv4l/asm.S

+/*
+ * Copyright (c) 2008 Mans Rullgard <mans@mansr.com>
+ *
+ * This file is part of FFmpeg.
+ *
+ * FFmpeg is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU Lesser General Public
+ * License as published by the Free Software Foundation; either
+ * version 2.1 of the License, or (at your option) any later version.
+ *
+ * FFmpeg is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+ * Lesser General Public License for more details.
+ *
+ * You should have received a copy of the GNU Lesser General Public
+ * License along with FFmpeg; if not, write to the Free Software
+ * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
+ */
+
+        .macro require8, val=1
+        .eabi_attribute 24, \val
+        .endm
+
+        .macro preserve8, val=1
+        .eabi_attribute 25, \val
+        .endm
+
+        .macro function name, export=0
+.if \export
+        .global \name
+.endif
+        .type   \name, %function
+        .func   \name
+\name:
+        .endm