make bitflags for integer conversion an enum (#283)

* make bitflags for integer conversion an enum

* typos

* tweak includes in tests and examples

---------

Co-authored-by: Laurence Lundblade <lgl@securitytheory.com>
diff --git a/example.c b/example.c
index 473e989..99944ff 100644
--- a/example.c
+++ b/example.c
@@ -14,7 +14,7 @@
 #include <stdio.h>
 #include "example.h"
 #include "qcbor/qcbor_encode.h"
-#include "qcbor/qcbor_decode.h"
+#include "qcbor/qcbor_main_decode.h"
 #include "qcbor/qcbor_spiffy_decode.h"
 #include "qcbor/qcbor_number_decode.h"