include, libctf: improve ECTF_DUPLICATE error message

It applies to enums now, so it should mention them.

include/
	* ctf-api.h (_CTF_ERRORS) ECTF_DUPLICATE]: Mention enums.
diff --git a/include/ctf-api.h b/include/ctf-api.h
index ad5add2..d3d8dbf 100644
--- a/include/ctf-api.h
+++ b/include/ctf-api.h
@@ -225,7 +225,7 @@
   _CTF_ITEM (ECTF_RDONLY, "CTF container is read-only.") \
   _CTF_ITEM (ECTF_DTFULL, "CTF type is full (no more members allowed).") \
   _CTF_ITEM (ECTF_FULL, "CTF container is full.") \
-  _CTF_ITEM (ECTF_DUPLICATE, "Duplicate member or variable name.") \
+  _CTF_ITEM (ECTF_DUPLICATE, "Duplicate member, enumerator, or variable name.") \
   _CTF_ITEM (ECTF_CONFLICT, "Conflicting type is already defined.") \
   _CTF_ITEM (ECTF_OVERROLLBACK, "Attempt to roll back past a ctf_update.") \
   _CTF_ITEM (ECTF_COMPRESS, "Failed to compress CTF data.") \