fix mention of prog.alt.c in 2015/burton/README.md

2015/burton/README.md

@@ -38,7 +38,7 @@ or
 
 ## Alternate code
 
-An alternate version of this entry, prog.alt.c, is provided.  This alternate code is discussed in the "prog.c vs prog.orig.c" section of the author's comments below.
+An alternate version of this entry, prog.alt.c, is provided.  This alternate code is discussed in the "prog.c vs prog.alt.c" section of the author's comments below.
 
 To compile this alternate version:
 
@@ -75,7 +75,7 @@ Printed in 8 pt Courier, it makes aesthetically pleasing 8.5 x 11 wall art.
 
 [1]: http://www.ioccc.org/2011/hou/hint.html "Hou Qiming"
 
-prog.c vs prog.orig.c
+prog.c vs prog.alt.c
 ---------------------
 
 Dominik Muth observed a syntax error on `1+1`, `1-1`, `1|1`, and `1^1` when using an