Fix assumption that EOF==-1 in 2015/schweikhardt

The author stated EOF must be -1 but this is, as the author even noted,
not guaranteed by the standard (it just has to be a value < 0).

But rather than add C pre-processor directives to force EOF to be -1
(preferred over changing EOF to -1 in the code) the Makefile does (after
${CFLAGS}) -UEOF -DEOF=-1 so as to not have to modify the code any.

A few fixes in the README.md file.

This should complete this entry, leaving just (I think) 2015/endoh1.

thanks-for-help.md

@@ -3919,7 +3919,12 @@ past).
 
 ## <a name="2015_schweikhardt"></a>[2015/endoh3](/2015/schweikhardt/prog.c) ([README.md](/2015/schweikhardt/README.md]))
 
-[Cody](#cody) added the [try.sh](2015/schweikhardt/try.sh) script.
+[Cody](#cody) fixed the build so that `EOF` will be `-1` as the program assumes
+this. It was decided by Cody to do `-UEOF -DEOF=-1` so as to not have to modify
+the code any with C preprocessor directives (the preferred way) or changing
+`EOF` to `-1`.
+
+Cody also added the [try.sh](2015/schweikhardt/try.sh) script.
 
 
 ## <a name="2015_yang"></a>[2015/yang](/2015/yang/prog.c) ([README.md](/2015/yang/README.md]))