Prep to move 1988-2004 entries into subdirs

Make changes to links impacted when we move 1988-2004 entries
from all of a year's winning entries in a single directory
to each winner being in their own sub-directory under the
given year directory.

2015/muth/machine_gcd.h

@@ -1,7 +1,7 @@
 /*
  * greatest common divisor
  *
- * based on http://www.ioccc.org/2001/herrmann1.gcd
+ * based on http://www.ioccc.org/2001/herrmann1/herrmann1.gcd
  */
 
 // try tape_15_50.h or tape_77_55.h

2015/muth/machine_times2.h

@@ -1,7 +1,7 @@
 /*
  * multiply by 2
  *
- * based on http://www.ioccc.org/2001/herrmann1.times2
+ * based on http://www.ioccc.org/2001/herrmann1/herrmann1.times2
  */
  
 // try tape_five.h