Filesystem: Include '.' and '..' in directory iteration

The standard is intentionally vague on if filesystems must
have '.' and '..' entries, allowing filesystems to omit this
concept completely:
http://pubs.opengroup.org/onlinepubs/9699919799/functions/readdir.html

However, the '.' and '..' entries are common on FAT filesystems
and in most other filesystems.

This enables '.' and '..' entries in the FAT filesystem.

Author: geky

features/TESTS/filesystem/fat_filesystem/main.cpp

@@ -116,7 +116,13 @@ void test_read_dir() {
     while ((de = readdir(&dir))) {
         printf("d_name: %.32s, d_type: %x\n", de->d_name, de->d_type);
 
-        if (strcmp(de->d_name, "test_dir") == 0) {
+        if (strcmp(de->d_name, ".") == 0) {
+            test_dir_found = true;
+            TEST_ASSERT_EQUAL(DT_DIR, de->d_type);
+        } else if (strcmp(de->d_name, "..") == 0) {
+            test_dir_found = true;
+            TEST_ASSERT_EQUAL(DT_DIR, de->d_type);
+        } else if (strcmp(de->d_name, "test_dir") == 0) {
             test_dir_found = true;
             TEST_ASSERT_EQUAL(DT_DIR, de->d_type);
         } else if (strcmp(de->d_name, "test_file") == 0) {

features/filesystem/fat/ChaN/ffconf.h

@@ -126,7 +126,7 @@
 /  When _LFN_UNICODE is 0, this option has no effect. */
 
 
-#define _FS_RPATH	0
+#define _FS_RPATH	1
 /* This option configures relative path feature.
 /
 /   0: Disable relative path feature and remove related functions.