t: switch $_x40 to $OID_REGEX

Switch all uses of $_x40 to $OID_REGEX so that they work correctly with
larger hashes.  This commit was created by using the following sed
command to modify all files in the t directory except t/test-lib.sh:

  sed -i 's/\$_x40/$OID_REGEX/g'

Signed-off-by: brian m. carlson <sandals@crustytoothpaste.net>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

t/t3100-ls-tree-restrict.sh

@@ -32,7 +32,7 @@ test_expect_success \
      echo $tree'
 
 test_output () {
-    sed -e "s/ $_x40	/ X	/" <current >check
+    sed -e "s/ $OID_REGEX	/ X	/" <current >check
     test_cmp expected check
 }