cleanup winner README.md files

Fixed cases where there was a bad trailing backslash.

Improved a few cases where a code block was needed
to highlight some text.

Changed a few cases where a code block needed to
declared as, say, a sh code block.

Fixed a few cases where the winner information was not properly formatted.

Plus a few nits and clarifying text was added.

2019/diels-grabsch2/README.md

@@ -75,7 +75,9 @@ are step 1 and step 2 achieved then?
 
 Regarding step 1, note that the large string literal
 
-	"`x{bh}ndbq..."
+```
+"`x{bh}ndbq..."
+```
 
 in the last line doesn't look like C code.  Moreover, it is too short
 to contain even a compressed representation of all preceding and