Make all doxygen '@' (#266)

Co-authored-by: Laurence Lundblade <lgl@securitytheory.com>
diff --git a/example.c b/example.c
index a6a0a13..c489ad6 100644
--- a/example.c
+++ b/example.c
@@ -130,7 +130,7 @@
  * @return  The pointer and length of the encoded CBOR or
  *          @ref NULLUsefulBufC on error.
  *
- * This encodes the input structure \c pEngine as a CBOR map of
+ * This encodes the input structure @c pEngine as a CBOR map of
  * label-value pairs. An array of float is one of the items in the
  * map.
  *