Add missing file in commit 017230

The file 2018/burton2/README.txt was added to the repo (it was the
file missing from the repo but I forgot to include it in the git commit
command).

2018/burton2/README.txt

@@ -0,0 +1,71 @@
+tac comes with a small suite of support programs to test and validate against.
+Untar tests and variations in the same dir as the sources,
+or change runtest and unob.sh to look elsewhere for the keyword and test files.
+
+keywords is a critical file, created from ioccc.kw.freq by mkkeywords.
+Only ioccc.kw.freq produces results compatible with iocccsize.c;
+however, any of the variations can be used instead:
+
+	mkkeywords c11 > keywords
+
+unob.sh uses the same input file as mkkeywords to control spaces after keywords.
+The script allows an environment variable, KW, to override this.
+Use it simply:
+
+	unob.sh prog.c | less
+	unob.sh -p prog.c | less
+	KW=c11 unob.sh prog.c | less
+
+To handle obscure command line defines, use the environment variable DEF:
+
+	DEF="-D'g(o)'='goto o;'" KW=c11 unob.sh -p prog.c | less
+
+It does an amazingly good job for such a simple script.
+
+Manifest
+
+prog.c                  the reason for this README
+keywords		the file #included in prog.c, output of mkkeywords
+mkkeywords		reads one of the files from variations, produces string for prog.c
+ioccc.kw.freq		keywords used by iocccsize, sorted by frequency in 201x ioccc winners
+unob.sh			a more robust unobfuscation script; requires variations/c11 in cur dir
+tokenfix		patches up prog -t output for ::, >>>, ...
+src.doc.rot13		the answers, or at least significant help
+tac.c			more clearly written code, offered as a replacement of iocccsize.c
+patch			fixes single quotes in iocccsize.c, adds #ifndef, removes "I"
+fixed_iocccsize.c	iocccsize with patch applied, and nop -c argument added
+
+tests/*
+runtest			script to run the tests; ./runtest | diff results -
+results			results without -k
+results.k		results with -k; opt=kcrs ./runtest | diff results.k -
+test*.c			various test cases looking for compatability
+iocccbug*.c		various test cases demonstrating problems with iocccsize
+spotcheck		script to test a lot of files vs iocccsize
+spotdiff		summarize the results of spotcheck, showing only differences
+discrepancies		text file of the differences found using all the ioccc winning entries
+
+to test prog:
+
+	runtest | diff - results
+	opt=kcrs runtest | diff - results.k
+	find ~/src/obc -type f -a -name "*.c" | xargs spotcheck prog
+		[ | spotdiff | diff -bw - discrepancies ]
+
+to test tac:
+
+	prog=tac runtest | diff - results
+	prog=tac opt=krs runtest | diff - results.k
+	find ~/src/obc -type f -a -name "*.c" | xargs spotcheck tac
+
+variations/*		as described in the remarks, and in each file below
+ansi	
+c++11
+c++14
+c++98
+c11
+c99
+java8
+kandr
+kandr2
+v7unix