Function types: Merge from trunk.

- [49980] adds tests with const result
- [53619] Cleanup function_types Jamfile. Fixes #1653 (maybe).
- [62827] Update Borland workarounds.  Fixes #3162.
- [70856] Rebuild documentation


[SVN r70861]

libs/function_types

@@ -1 +1 @@
-Subproject commit 7e239167da7666a40bf6bd1faf4c5ea9c28f5d96
+Subproject commit 1f2bc4d8d321c7fc3e2c02236cb5f0917ab49f4a