Use SECTION_TEXT instead of section .text for the compatibility

aout does not support 'align='.
Signed-off-by: Michael Niedermayer <michaelni@gmx.at>

libavcodec/x86/pngdsp.asm

@@ -28,7 +28,7 @@ SECTION_RODATA
 
 cextern pw_255
 
-section .text align=16
+SECTION_TEXT 16
 
 ; %1 = nr. of xmm registers used
 %macro ADD_BYTES_FN 1