add make genpath rules, .path files, updated .top and .year

Add .path files to each winner directory: a file containing
the path to the winner directory from the top directory.

Changed YYYY/.year files to contain the paths, from the top
directory, if the winning directories for the given year.

Changed `/.top` to contain the IOCCC years.

Added `make genpath` rule to the top Makefile and the
year Makefiles to generate the above.

Added FAQ 6.8 to `faq.md` to explain the above.

Updated manifest to reflect recent changes to the list of files.

2012/.year

@@ -1 +1,14 @@
-2012
+2012/blakely
+2012/deckmyn
+2012/dlowe
+2012/endoh1
+2012/endoh2
+2012/grothe
+2012/hamano
+2012/hou
+2012/kang
+2012/konno
+2012/omoikane
+2012/tromp
+2012/vik
+2012/zeitak