doc: Trim .txt files trailing whitespace

via OSX: find . -name '*.txt' -exec sed -i '' -E 's/[[:space:]]+$//' {} +

doc/manual/special_ops.txt

@@ -34,7 +34,7 @@ templates and macros), depending on the desired effect:
 The following dot operators are available:
 
 operator `.`
------------- 
+------------
 This operator will be matched against both field accesses and method calls.
 
 operator `.()`