t0050: fix printf format strings for portability

Unlike bash and ksh, dash passes through hexadecimal \xcc escapes.
So when run with dash, these tests *pass* (since '\xcc' is a perfectly
reasonable filename) but they are not testing what was intended.

Use octal escapes instead, in the spirit of v1.6.1-rc1~55^2
(2008-11-09).

Reported-by: Ramsay Jones <ramsay@ramsay1.demon.co.uk>
Signed-off-by: Jonathan Nieder <jrnieder@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

t/t0050-filesystem.sh

@@ -4,8 +4,8 @@ test_description='Various filesystem issues'
 
 . ./test-lib.sh
 
-auml=`printf '\xc3\xa4'`
-aumlcdiar=`printf '\x61\xcc\x88'`
+auml=$(printf '\303\244')
+aumlcdiar=$(printf '\141\314\210')
 
 case_insensitive=
 unibad=