Add 2019/diels-grabsch2/try.sh script

The try.sh script looks for sha512sum and shasum. If either of these are
found it will use the one found (in the order of sha512sum first and
shasum -a 512 second) and prog. If neither can be found it uses just
prog. If one of them can be found, however, it shows how the output is
the same.

The prog.c was restored from prog.orig.c. Like 2019/diels-grabsch1 the
purpose is no longer valid and even more problematic is the fact that
the checksum value obviously would not be correct otherwise. Makefile
updated instead.

The README.md file has been format/typo checked.

.gitignore updated - added files that try.sh script uses (though it does
delete them after use).

2019/diels-grabsch2/Makefile

@@ -38,7 +38,7 @@ include ../../var.mk
 
 # Common C compiler warnings to silence
 #
-CSILENCE=
+CSILENCE= -Wno-strict-prototypes
 
 # Common C compiler warning flags
 #