Add/improve PPC64 support. On such machines, "uname -m" returns "ppc64,

so recognize them as such.


git-svn-id: file:///var/local/repositories/ffmpeg/trunk@5728 9553f0bf-9b14-0410-a0b8-cfaf0461ba5b

configure

@@ -365,7 +365,7 @@ case "$cpu" in
   alpha)
     cpu="alpha"
   ;;
-  "Power Macintosh"|ppc|powerpc)
+  "Power Macintosh"|ppc|ppc64|powerpc)
     cpu="powerpc"
   ;;
   mips|mipsel|IP*)