Added comments

TSRM/tsrm_virtual_cwd.h

@@ -186,9 +186,12 @@ CWD_API int virtual_chmod(const char *filename, mode_t mode TSRMLS_DC);
 CWD_API int virtual_chown(const char *filename, uid_t owner, gid_t group, int link TSRMLS_DC);
 #endif
 
-#define CWD_EXPAND   0
-#define CWD_FILEPATH 1
-#define CWD_REALPATH 2
+/* One of the following constants must be used as the last argument 
+   in virtual_file_ex() call. */
+
+#define CWD_EXPAND   0 /* expand "." and ".." but dont resolve symlinks      */
+#define CWD_FILEPATH 1 /* resolve symlinks if file is exist otherwise expand */
+#define CWD_REALPATH 2 /* call realpath(), resolve symlinks. File must exist */
 
 CWD_API int virtual_file_ex(cwd_state *state, const char *path, verify_path_func verify_path, int use_realpath);