Update 1984 README.md files and one Makefile

Just some clean up and general notes as well as add a 'To run:' section
to each README.md.

1984/decot/Makefile

@@ -185,8 +185,7 @@ all: ${DATA} ${TARGET}
 	supernova deep_magic magic charon pluto
 
 ${PROG}: ${PROG}.c
-	@echo "NOTE: This entry will not compile when using clang because it does not support"
-	@echo "      -traditional-cpp but it should compile with gcc."
+	@echo "NOTE: this entry requires a compiler that supports -traditional-cpp."
 	${CC} ${CFLAGS} $< -o $@ ${LIBS}
 
 # alternative executable

1984/decot/README.md

@@ -11,6 +11,10 @@ clang does not support. We thank Yusuke Endoh for his patch which allows the
 entry to compile under gcc! Please be advised that gcc under macOS is actually
 clang so this will not compile with the default gcc under macOS.
 
+## To run:
+
+	./decot
+
 ## Judges' comments: