MINOR: qpack: add ABORT_NOW on unimplemented decoding

Post-base indices is not supported at the moment for decoding. This
should never be encountered as it is only used with a dynamic table.
However, haproxy deactivates support for the dynamic table via its
SETTINGS.

Use ABORT_NOW() if this situation happens anyway. This should help
debugging instead of silently failed without error reporting.
diff --git a/src/qpack-dec.c b/src/qpack-dec.c
index 5546590..aac35a6 100644
--- a/src/qpack-dec.c
+++ b/src/qpack-dec.c
@@ -212,7 +212,15 @@
 		qpack_debug_printf(stderr, "efl_type=0x%02x\n", efl_type);
 
 		if (efl_type == QPACK_LFL_WPBNM) {
-			/* Literal field line with post-base name reference */
+			/* Literal field line with post-base name reference
+			 *
+			 * TODO not implemented
+			 *
+			 * For the moment, this should never happen as
+			 * currently we do not support dynamic table insertion
+			 * and specify an empty table size.
+			 */
+#if 0
 			uint64_t index __maybe_unused, length;
 			unsigned int n __maybe_unused, h __maybe_unused;
 
@@ -242,12 +250,21 @@
 				goto out;
 			}
 
-			/* XXX Value string XXX */
 			raw += length;
 			len -= length;
+#endif
+			ABORT_NOW(); /* dynamic table not supported */
 		}
 		else if (efl_type == QPACK_IFL_WPBI) {
-			/* Indexed field line with post-base index */
+			/* Indexed field line with post-base index
+			 *
+			 * TODO not implemented
+			 *
+			 * For the moment, this should never happen as
+			 * currently we do not support dynamic table insertion
+			 * and specify an empty table size.
+			 */
+#if 0
 			uint64_t index __maybe_unused;
 
 			qpack_debug_printf(stderr, "indexed field line with post-base index:");
@@ -259,6 +276,8 @@
 			}
 
 			qpack_debug_printf(stderr, " index=%llu", (unsigned long long)index);
+#endif
+			ABORT_NOW(); /* dynamic table not supported */
 		}
 		else if (efl_type & QPACK_IFL_BIT) {
 			/* Indexed field line */