Fix #4799. The same bug occurred in three places. One of these may have been the source of reported problems with remove_all. Several other problems in documentation and tests were also found and will be addressed separately.

[SVN r65765]

libs/filesystem

@@ -1 +1 @@
-Subproject commit 2a205e364ca1563f51916567ecec41c6952c35c8
+Subproject commit 47c7ac469966593485e00f554e1f2486c66b8f32